Is what will be the biggest complaint in Halo 4. Just an early prediction.
I'm pretty sure they will implement a system where credits are earned and spent on gun upgrades. This will not only offset the balance of play(as in CoD) but will upset the halo die hards.
343 will not learn from the mistakes of Reach but instead build upon them. The FPS multiplayer scene is evolving and it wouldn't make sense to bring back the relatively simple gameplay of old. It simply wouldn't sell.
I wouldn't like to be developing H4, pleasing the true fans will only dampen sales... whilst catering to casuals will be a losing battle as CoD has already got that audience.
The franchise can learn a lot from the demise of Reach, the halo obsession is officially over. We can also learn that the casuals are not interested long term and competitive players are equally put off.
I expect to see the return of old favorites in terms of maps and weapons but not in the way they are remembered. Sad times ahead.