Yes, AMXX will work with SC 5.0. But beware, people have reported bugs and instability issues with it.
Also, make sure to use Metamod-P Solokiller posted on SC forums instead of the default one that comes packaged with AMXX. And someone actually released the new Metamod's code, so it would be smart to recompile AMXX against it, I don't think anyone has done it yet on SC forums.
And there is a player management plugin packaged with SC 5.0, but I am not sure if it is turned on by default. SC 5.0 has added AngelScript as a new scripting language, and it would be better if you used AS plugins instead of AMXX.