Considering the isolation of the Crimean Gothic communities it was likely that at the time of extinction it could well have been multiple languages depending on how people measure the whole language/dialect thing....
Maybe a scenario such as those Goths who convert to Islam keep using Gothic as so it becomes what we would call Tatar today but from a different origin with a equally massive Turkic influence by atl 2018. Another group could arise resisting the Turkic-Islamic influence and potentially becoming what we would consider to be Cossacks. While Russian would also replace it to a great degree, Gothic would remain the de facto language of the regiment and their kin. Straight away we have two modern Gothic languages. For more maybe we could see an earlier expulsion of these Gothic Tartars and as a group they are divided in multiple directions. Therefore we could have by the present day multiple highly divergent dialects in Turkey, Siberia and likely Central Asia. That could give you four related though all uniquely descendants of Gothic with very little butterflies (assumedly).
Certainly the Alps could provide for maybe a handful of villages speaking Gothic and or Burgundian much like we have Romansh otl. Maybe a group of descendants of Visigoths could survive somewhere in Asturias or even in say Andorra.
That wouldn't avoid Russian conquest and gradual assimilation to Russians. Better would be keep Crimea as part of Byzantine Empire and avoid its decline and fall.