OK, there's a Warzone with about 200-300 people in it regularly. Not many, but enough to find full games.
Just to see if my impressions were correct, I played KZ3 for about an hour last night. Yes, the classes are still hideously unbalanced, TSPs are still dumb, the SMGs still stink, taking out a chump in an exo with an RPG is still hilarious, and Turbine is still the worst map in the history of multiplayer, but three notes:
1. KZ3 has better audio than Shadow Fall. It's way better, especially the gun sounds.
2. I vastly prefer KZ2/3's art direction over SF's. Those games had personality. There are no visual cues making SF look unique, none of the grit and grain that had been the series trademark.
3. Indeed, the graphics of KZ3 are not jarringly worse than SF. KZ3 already looked lifelike and realistic. True, its 30 fps was inconsistent, and the lighting wasn't gamma-correct. But it already looked really, really good. I think we're at the point where your budget, time, and talent are more of a limit on visual quality than the hardware.