From what I've read, and what's been posted here, here's why Huxley won't replace PS.
1. The battles are instance battles. CS anyone? maybe more BF2?
2. No persistent world. Everyone does that.
3. When you start the game, you can't go everywhere and you don't have the option to "cert" everything. No, not like PS where the only thing you can't immediately cert is BFR.
4. This game will be based on the Unreal 3 Engine, so those of use without massive computers, or similarly large budgets for new computers will get a game that runs poorly and has OK graphics. We already have that with PS.
5. The largest possible battle is 60 vs 60 (maybe not that but 120 total people). Major step down from 133 vs 133 vs 133.
6. You must gain 10 levels to get the next "cert", not just one to four like with PS and that's assuming you won't drop anything to get that new one earlier.
Given these reasons, and the FACT that it is not a true MMOFPS but simply a lot of dedicated servers running a pretty Counter Strike with "certs", Huxley will not replace, nor even be in the same genre as PlanetSide.
PS I use the word "cert" with quotes because I can't remember the word they used but it essentially functions the same way.
PPS For more info check out,
http://www.huxleygame.com/ It was my source, along with this thread for what I posted.