About limits: It's true some people have to try harder than others, and some people are destined to be better than others. However, if it was this simple, we would see much more consistent results from our top level players. We've seen some pretty big upsets which, statistically, make no sense - Coney 3-stocking M2K, DEHF losing to Espy, etc. Think about DEHF - he can beat M2K, largely considered the best MK, most of the time, yet he lost to Espy, a Sonic player. We can see from watching Espy and M2K that the are both near their limit and of about equal skill. Why, then, did DEHF lose to Espy?
Tiertastically, speaking, this is an impossible upset. However, this just shows what a big difference the player's style can make. DEHF is great at the MK MU, but not at the Sonic MU. He may have nearly reached his limit for the MK MU, but he can definitely improve vs. Sonic. He may be near his limit, but there is definite room for improvement, no?
Another factor is mindgames and predictions. If the opponent has 10x your experience, the match is still very winnable. Imagine if you will, a Brawl player who could read minds and impulses. In his case, even Ganon vs MK becomes 100:0, even if the MK has reached the maximum human potential. There are plenty of factors to make the 'limit' fairly insignificant. At the very least, we can see the limit is set pretty high. In a 55:45 MU, with both players equal skill, the one with the advantage would hypothetically win every time. MK has no bad MUs, so why doesn't MK win every tourney? Because M2K won't change his predictable style and is quickly becoming a thing of the past. I mean, MK WILL win every tourney now that Ally mains him. Errr... because of unique mindgames and playstyles, each with their own strengths and weaknesses.
tl:dr - Limits are mostly insignificant. Adapting to your opponent can more than compensate for such small differences in skill.
Also, has anyone seen DEHF? I haven't heard anything since he claimed he would start maining ICs. I really doubt he'll do that, but with Ally switching mains, players quitting Brawl for P:M, and that last post of his, I can't help but worry a little.