I think it's hard to judge without seeing the "Legacy" army lists. Right now, for me I don't see a ton to get upset about because we haven't seen the lists. Other side of the coin, I have all "Legacy" army and I haven't seen anything about the lists, so there's not a ton for me (personal opinion) to be excited for yet.
I think most people are worried that Legacy armies without "support" from GW will either enter the game in a really overpowered or underpowered state and won't receive any adjustments to compensate them one way or the other, and that it will rely on the community to police the game. GW has been known for this in the past, but since ToW is being done by the Specialist Games team and they have a really good track record with things like HH and MESBG, I think I would lean slightly towards optimistic on this one.
Excited to see what the game is going to bring for us "Legacy" players though!