I'm not sure about 343 doing something else first, but it does seem to me that Halo 4 could have used more time in development. Gameplay wise they were going up against one of the finest single player combat experiences ever made. The Prometheans just didn't stand up. They were unmotivated and boring. Story wise their villain, while cool and nuanced in the books was flat and comically uninteresting in game. And in graphics and technical things like level size it was pretty obvious that Halo 4 needed more than the 360. It pulled off some neat tricks, but would have been better served by tons more memory and processing power.

Giving them the extra year and letting them target the next Xbox might have provided enough time to clean up the story and gameplay. Still they did a decent job, and maybe they will now have the experience and hardware they need to make Halo 5 a truly great.