Halo 2 didn't have Forge or any "custom content community" that I can think of, and yet it's the Halo I had most fun with. I think it was and is the best Halo so far. The communities had nothing to do with that. So if you think 343 "monopolizing everything" is honestly reason enough to conclude that Halo 4 will suck... Well, then I can't take what you say very seriously.
If not for Anniversary and the Title Updates, I probably would have quit Reach a long time ago. Default Reach is just not fun. The fact that 343 is trying to make a game, of which they didn't even make, better with any updates at all says a lot of good things about them, I think. Why should they even try to make Halo Reach perfect if it's already their job to make three more Halos?
What makes people think that Halo was in better hands with Bungie? The features? Seriously? 343 is "just getting started". 343 can't just copy and paste all the features that Bungie added over years in just a few months. Not to mention that Bungie didn't lift a finger to fix their own game. They do not care about any of you.
343 is a company. A company that's trying to make a whole new video game, fix Reach little by little, and put together a website that will work for all Halo fans. The mature thing would probably be to bare with them, wait for results, and write out some constructive criticism every now and then. What the majority of you do is complain, spit on 343's attempts to do...everything that they're trying to put together, insult them, and complain some more.
Grow up. Stop being a bunch of drama queens.