Jordanes' accounts should really be taken with a grain of salt and due caution when it comes to Gothic history before they crossed the Danube. Cassiodorus (the author of the original text Jordanes shortened and rewrote) wrote a Gothic history that had the objective to legitimize a posteriori their existence as peoples, and critically trough their history in a Late Roman fashion, as only "real" peoples had an history as far as Romans were concerned; Barbarians (especially in the European Barbaricum) living in an extended present. People writing for Barbarians or Barbarian scholars themselves had to assert they did have an history, and a prestigious one at that.
This wasn't particular to Goths, and Barbarian "origin myth" is almost a genre on its own : the Advent of the Saxons, where whole kingdoms just translated from Germania to England in one piece; Frankish Trojan origin with sea monster progenitors for the most famous, borrowing heavily from the late ancient best-stellers when it came to the story of the origins : Virgil' Aeneid and the biblical Exodus; with a touch of classical sources such as Tacitus' Germania.

Jordanes' Gaetica might not be the most fanciful or fantastic account of these, but how much does it hold up?
Not that bad, actually : there's some mistakes (such as when he identifies Gaetes as Goths), but the Greuthingi Goths gained an almost immediate importance and prestige even before the late IVth century as they obtained some form of hegemony beyond the Danube, and Tervingi successful conflict with Romans in the late IVth and early Vth century gave them immediate recognition (compared to light-weighted Franks, whom ruling dynasty in the late Vth couldn't even hope such historicity).

At first glance, his description of migration from Scandza (identified as Scandinavia or the island of Gotland) and, from the Vistula, to a pluri-centenial errance into the Barbaricum until finding a promised Land seems attested by archeology, all points which made Jordanes taken rather seriously until the mid-XXth century. Up to a recent past, Gothic migrations were depicted precisely on a map, showing their peregrinations in Barbaricum and Romania.

But while the parts covering Gothic history with Romans are generally trustworthy, and as Cassiodorus (and Jordanes) could look at other contemporary sources; they couldn't do so with Gothic history before the IVth century, and had to make due with an oral history of a people which was increasingly Romanized since centuries. It doesn't help Jordanes' Getica is a summary, and several aspects are rushed, shortened or cut from the original version.
The Scandinavian origins are more or less brushed quickly, Scandza and Gothiscandza (the name Goths gave to their new homeland in Poland) looking a bit out of place in the setting they're supposed to happen as the narration of the migration quickly follows with a mix of various peoples from various sources and various times : maybe supported by an orally-transmitted memory, the origin of Goths in modern Poland is still pretty much drowned in a quite Roman conception of a "long present" of the Barbaricum. Scandza is essentially the mother of all inhospitable places, where all people live as cavemen, and that anyone wishes to leave; and a more serious alternative to Britain as the urheimat of Goths according Jordanes (especially as Belisarius proposed Goths to migrate there during the wars), and as vaguely located in the North as was Thule, the urheimat of Heruli.

Does that means that the Scandinavian origin of Goths is entierely bogus or unproven?
It remains possible, but it is heavily disputed.
The presence of stone circles and similar weaponry or jewellery in Northern Poland, Germany and Sweden; while often used to argue in favour of a migration in the Ist to IInd centuries, might as well be the trace of stronger contacts and cultural "borrowing" between these zones. It's possible that the people of the Wielbark Culture were the same than the previous and neighbouring Przeworsk culture, just changing their habits and references. On a strictly material ground, it's is particularly hard, if not impossible, to tell the difference.
Linguistic analysis of Gothic, furthermore, doesn't highlight a particularily close relationship to Scandinavian Germanic ensemble, and it appears closer to central Germanic languages overall. Of course, it goes both ways, and it might be a sign of acculturation of newcomers into a relatively close linguistic and social ensemble. But the model of a Scandinavian origin of Goths as an already formed people suffers from this.
Gothones are already mentioned in the region by Tacitus, but that's before the big changes of the Wielbark culture are really widespread : it might be the sign of an "indigenous" origin of Goths as, if most probably not as a coherent people, maybe a regional super-identity.

Migration or not, in any way, there is archaeological and historical elements for a more tight connection between southern Scandinavia and northern Germania at the turn of the millennium; and these contacts might have fuelled a traditional history, carried and evolving with groups eventually forming Goths of Late Antiquity.