Going to call it now: I think Vayne is going to become popular this patch
There are so many indirect buffs and meta changes that favor her this patch that I would be surprised if she didn't become somewhat of a meta pick. If tanks become stronger due to the reworks and item changes, she directly counters them with her silver bolts. The changes to crit item costs will only help her reach her lategame even earlier. I also think the shiv/rapidfire cannon combo will become her new burst build, like the IE/Shiv build we had a few months ago.
The only reason this may not be a thing is Lucian being meta.