There is a reason game play didn't substantially change between CE/2/3 as opposed to Reach and now Halo 4. It's not about "change". You want changes that complement Halo. Usually, it's in the form of crazy new game types, new weapons, new vehicles and maps.
After Halo 5, we'll have had as many radically changed Halo games as "classic" ones. Also, MCC has been irreparably screwed by the launch. The player population is probably 1/10th what it was at launch. Every Halo release cannibalizes the game before, so it doesn't even matter if it works 5 months from now as much, because most people will leave to play Halo 5. It's always been like that. Most people would consider Reach worse than Halo 3, and yet they still left to play it just the same.
But that's why we have the beta now. We can see whether we like the game or not. Josh is a good guy and humble enough to accept criticism. He's probably reading these posts. Let's hope they take constructive criticism well, ignore the hateful trolls and insults. We're not the only ones playing this game. Halo 5 will be the first game for a new generation of fans as well. Will be nice to see how it plays out. I'm more pessimistic than optimistic based on just the past 4 years of Halo game play/fanbase apathy. But we'll see.