Once the meta comes around again, she'll be facerolling again.
No, she won't. This year, we've seen tanky metas with sticky champions, we've had metas nearly absent of assassins, and we've seen nerfs to the early game AD carries that Vayne typically struggles to deal with. Fact is, this year has had great metas for Vayne. It's exactly what she wants, and despite that, she sucks. There is no "meta shift" that's bringing her back.
She's one of the worst AD carries in the game right now. You have Corki and Kalista who are worse than her, and aside from that she's bottom-tier. Even among people who main her, she's not breaking a 50% winrate. She's bad, through and through.
The big reason for this is because they nerfed her items, nerfed her slightly, and buffed the items that other AD carries like more than she does. You can't just dismiss the effect that this had on her. It's not something a meta change is going to miraculously fix.
The other reason they're buffing her is because they accidentally nerfed her. The recent bugfix to the way her Q interacted with crit actually decreased her expected dps in most scenarios, which resulted in the winrate drop we see in patch 6.15 (and before you ask, we can't ascribe this to more people playing her again, because her playrate was virtually unchanged and we're still seeing the decreased winrate this patch).
I'd understand if you were upset about them buffing her because you hate her design. That would be fair. A lot of people are annoyed by Vayne's design. However, if you think she's still good nowadays, then you really don't have a great eye on her balance. I think you're letting personal dislike for her taint your opinion.
Seriously dude, it's a pretty minor buff to a bad champion. It's not the end of the world.