While a Pixar Land could be made that is wonderful, the problem is that the Pixar Movies do not exist in the same world (fan theories notwithstanding).
A land with rides for A Bug's Life, Toy Story, and Inside Out will leave you wondering if you're the size of a bug, toy, or human. A land with rides for WALL*E, Brave, and Up will leave you wondering if you're in the past, present, or future. Sure, you can cherry pick a few that 'go together', but you'll wind up with someone crying that their favorite isn't included because of some artificial commitment to a thematic land.
And so, a Pixar Land will have to forego a unified theme except for a big Pixar Animation sign. Now, can a really nice 'land' be made from that? Yes. Will it be Magic Kingdom 2? Oh, most definitely. Even worse. MK divides their rides into thematic lands: fantasy here, adventure here, sci-fi here. A Pixar Land will either have to re-create that approach and be exactly like MK, or, just a jumble of movie facades as you pass each IP-based ride.