As a Link main, I'd probably say that I'd still play Melee for its unique qualities but admittedly only high tiers would reduce some of my enthusiasm for the game. I'd most likely switch to Smash 4 primarily (right now I'm 2/3 Melee and 1/3 Sm4sh) because of the larger character selection it would bring, that's the only reason I play Sm4sh at all. However, Melee is such a better game to watch and play in my opinion that It would still likely see much playtime; that, and the vast majority of tournament matches are already pretty much restricted to the Top 8 anyway so not having the lower characters wouldn't affect high level play as much as some people think. I'd probably end up switching to Sheik or Falcon most likely, since I can't stand Fox or Marth.
Also, it is perhaps a generalization to say players only main mid-tiers at worst; you can probably define over half the roster as mid-tier, so where do you make the cut? There's probably a good difference between maining say Samus or Pika who is pretty high up there (but some call him mid tier due to being outside the Top 8) and someone like DK or Mario who is on the low end of that list. I think that outside the Top 8, character selection for a player is largely based on fanboyism or just having that character work better with the player despite the drawbacks.
