User blog comment:TheUnknown285/Bioware releases teaser trailer of Mass Effect 4/@comment-4121017-20140614001902/@comment-4950455-20140614082435

Not at all sure where you're getting that "likely" non-import Shepard from. The previous non-import Shepards aren't a good comparison because they were intentionally suboptimal in order to reward players for playing the previous game(s). Everything we've heard indicates that if ME:Next is a sequel at all, it still won't be a continuation, so I doubt they'll follow that same model. I think whatever decisions Bioware sets in canon will be those which offer the most story possibilities, which previous default decisions largely don't.

And while someone could theoretically build new geth, they probably wouldn't be "the" geth.