Based on latest linguistic, runic and genetic evidence, it seems that the widely held theory of a Gothic migration from Scandinavia to what eventually became Poland is a myth. Indeed, perhaps the Goths didn't originate in Scandinavia, and never even set foot there? Consider the following...
Runologists from Sophus Bugge (1866–67) to, most recently, Edith Marold (2010) have claimed that there was a Gothic (East Germanic) linguistic element amongst the older futhark inscriptions of Scandinavia. In the present paper, this claim is viewed against a horizon of nineteenth-century Danish and Swedish nationalism, where “Goths” and “Gothic” became politically sensitive terms in view of the purported emigration of the Goths from a homeland in Scandinavia. This is followed by a discussion of the linguistic assumptions underlying the classification of some of the early Scandinavian inscriptions as Gothic, assumptions which (with Peterson 1998) are all rejected — including Marold’s recent insistence on the final -a of the Etelhem clasp form wrta ’created’ being a Gothic 3 pt. sg. ind. ending, cf. Gothic waúrhta ‘worked’. It is argued that this -a is as likely to reflect an Old High German (or even West Germanic) suffix, cf. OHG frumita ‘(he) furthered’.If the most common Germanic loanwords in Proto-Slavic are of West Germanic origin, then where did these contacts take place and what happened to the Goths? I'd say the Proto-Slavs and West Germanic tribes mingled west of the Oder, in what today is eastern Germany. On the other hand, the early Slavs of Southern Poland were largely separated from the Goths by the Carpathians, because the latter were a people of the Roman Frontier. That's why archeological items with Gothic runes have never been located in Poland, but apparently they have turned up in Hungary, Romania and Ukraine.
Nielsen, Hans Frede, Gothic Runic Inscriptions in Scandinavia?, 2012, Futhark: International Journal of Runic Studies (ISSN 1892-0950)
This dissertation provides a thorough review of the words belonging to the oldest layer of Germanic loanwords in Proto-Slavic and answers the question of how these words were adapted to the Proto-Slavic accentual system. The dissertation contains a corpus of 78 words that can be regarded as Germanic loanwords in Proto-Slavic. The discussion of the etymology of these words is followed by a comprehensive linguistic analysis of the material, focussing on formal clues for establishing the Germanic donor language of the Slavic forms. It was found that, contrary to earlier ideas, West Germanic loanwords are more numerous in Proto-Slavic than Gothic loanwords. It turned out that there is even a small number of loanwords from Low German in Proto-Slavic. Research into the accentuation of the loanwords has resulted in the establishment of a distribution of the words over the three Proto-Slavic accent paradigms (a), (b) and (c). It is concluded that accent paradigm (b) was the “default” accent paradigm for Germanic loanwords when they were adapted to the Proto-Slavic phonological system, as opposed to all earlier theories, which assume that Germanic loanwords regularly joined accent paradigm (a). The only loanwords that did not generally take accent paradigm (b) are loanwords with a long vowel in a stressed heavy syllable, which under certain conditions discussed in the dissertation adopted accent paradigm (a).
Pronk-Tiethoff, Saskia Elisabeth, The Germanic loanwords in Proto-Slavic: origin and accentuation, 2012, Doctoral Thesis, Leiden University
Linguists like Frederik Kortlandt knew something was rotten with the standard view of who the Goths were and where they came from more than a decade ago. The following excerpt comes from Kortlandt's The Origins of the Goths, published in 2000.
Witold Mańczak has argued that Gothic is closer to Upper German than to Middle German, closer to High German than to Low German, closer to German than to Scandinavian, closer to Danish than to Swedish, and that the original homeland of the Goths must therefore be located in the southernmost part of the Germanic territories, not in Scandinavia (1982, 1984, 1987a, 1987b, 1992). I think that his argument is correct and that it is time to abandon Iordanes’ classic view that the Goths came from Scandinavia.
There is no archaeological evidence for a large-scale migration of Goths from the Baltic to the Black Sea (cf. Heather 1991: 6 and Hachmann 1970: 467). In fact, there are several reasons why such a migration is highly unlikely. First of all, there is a clear discontinuity between the Przeworsk culture in Poland and the Černjahov culture in the Ukraine which are identified with the Goths before and after the migration, respectively (see the map of Green 1998: xiv). The only reason to assume that the Goths followed the rivers Bug or San and Dniestr is that “the terrain did not offer many alternatives between a common starting-point and a shared goal” (Green 1998: 166). Secondly, the territory between these two areas north of the Carpathian mountains is precisely the homeland of the Slavs, who do not appear to have stirred before the arrival of the Huns in the fourth century. This can hardly be reconciled with a major migration of Goths through their territory. Thirdly, the periodic exposure to severe stress in the fragile borderland communities of the steppe prompted westward population movements toward areas of more stable climatic conditions. An eastward migration of Goths from the richer upland forest into the poorer lowland steppe was both unmotivated and difficult to realize against the natural forces to be encountered. Fourthly, the expected direction of a migration is toward more developed areas where life seems to be better, which in the present context means toward the nearest border of the Roman Empire. We would therefore expect the Goths to move to the south through the Moravian Gate toward the Danube, as did the Slavs a few centuries later. Fifthly, there is little reason to assume that the Goths behaved differently from the Burgundians, the Vandals, the Marcomanns and the Langobards, all of whom crossed the upper Danube at some stage. It therefore seems probable to me that the historical Goths followed the course of the Danube downstream and entered the Ukraine from the southwest.
The map above depicts Europe in the 1st Century AD, as per Roman geographer Pomponius Mela (source: Wikipedia), and backs up Kortlandt's position by failing to show any Germanic tribes near the Vistula. The final nail in the coffin for the theory of Goths in Poland would be a lack of typically Scandinavian Y-DNA markers, like I1 and R1a-Z284, in remains from the purportedly Gothic Wielbark Culture of the Vistula basin. I have a hunch this crucial evidence is on its way, thanks to a new ancient DNA lab in Poznan (see here for the story in Polish).
Russian mtDNA, Goths of the Ukrainian steppe, and a proto-Slavic expansion from present-day Poland (Morozova et al. 2011)
First direct evidence of genetic continuity in West and Central Poland from the Iron Age to the present
The history of Slavs inferred from complete mitochondrial genome sequences