Hmmm, I have mixed opinions.
Truthfully I've already seen games where you have a finite number of enemies, they follow a schedule, and once they are dead they stay dead (you can keep walking over their body if you go through a room or hub a lot). It's a decent way to limit resources and such in a game.
However, by the same token this would seem to imply that they are moving away from a real "twitch shooter" because part of what allowed that kind of enviroment was the practically unlimited enemies and resources to kill them with, ensuring a non-stop bloodbath.
With no offense to ID there are only 3 ways to do a game:
#1: Spawn Points (ie Monster Closets)
#2: Finite Enemies in specific locations
#3: Random spawn throughout a level as opposed to a specific location. This leads to games where you find monsters glitched into walls once in a while (and similar things).
Now, maybe ID has come up with something totally new, but I sort of doubt it. The vibe they seem to be pushing with Rage seems to be more along the lines of #2. Though perhaps with scripted spawns after specific events.