Some will probably, you can see a bunch of previous TI winners still playing cause they probably don't have much else to do anyway, and to some extent it's "free". Like if you have enough money you don't need to work anymore and you still like playing dota, makes sense to keep playing professionally and making some money even if you never win TI again. Better than playing pubs with retards. Look at Puppey or Kuroky, been playing since dota1, both have won a lot of money(Kuroky especially, he's the highest on the list besides the 5 OG players who won 2 TIs but Puppey runs Secret so he might be making even more money outside of prizepools) but they're still playing competitively. They'll only quit when they feel they can't play at a pro level anymore/the scene dies, no reason for them to fully retire I think, unless you really hate the grind(which I'm sure some people hate, like Ana).