he is referring to the marksman changes coming up in the preseason. riot has already said like a thousand times they don't have any information on what they plan to do just yet. they are still working on preliminary stuff. and will announce it a few patches from now. most likely a little after worlds or near the very end of it.
just be patient. you will have your info.
vayne is definitely going to be touched though. and my guess is that judging by the one nerf they do have they realize that her early game laning is too strong relative to how strong her late game is so they will probably nerf her early game while keeping her identity as a duelist/late game hyper carry in tact.
i would also suspect they would keep her silver bolts true damage the way it is because she exists to counter an all tanky comp. she is a great pick into comps that are heavy in armor like shen, malphite, volibear, etc all on the same team with maybe even an urgot adc would be a nightmare for most adcs, but vayne its not as big of an issue.