Iirc there was a sign pointing to it happening in early 2021, because Capcom announced that the winner of Capcom Cup 2020 won't automatically qualify for it 2021. The last time this happened was in the transition year from SF4 to SF5, where Kazunoko won Capcom Cup for SF4, but next year they no longer had SF4 on the Pro Tour (which starts early in the year), only SF5. And his win in SF4 didn't qualify him for a SF5 finals for obvious reasons.
But looking at their roadmap for SFV, it's hard to imagine they would launch SF6 during all of this.
Agreed, I would think it'd be better to push SF6 to at least 2022. Seems like they're not quite done with SF5 anyways.