Fortunately the PC servers are completely controlled by IllFonic and will continue on. While it's possible they could buy the Xbox 360 servers from THQ, they "cannot justify the cost" right now.
The studio points out that purchase of Nexuiz on XBLA should be avoided and the title pulled from the store. The developer gets no money from any of those purchases.
"As some of you know, the Xbox Servers are now offline," IllFonic on their Facebook page.
"It was fun while it lasted on there and we are glad you guys enjoyed the game! Unfortunately, the Xbox Servers were controlled by THQ and in the current state, cannot be maintained anymore. Since the PC servers are different and can be controlled 100% by IllFonic, they will remain online and functional.”
As you can imagine the Xbox 360 fan base for Nexuiz was notably upset, but IllFonic dispelled any notion that they were in control of the situation, or were continuing to profit from it.
"Anyone who buys Nexuiz on XBLA would be sending money to THQ, not IllFonic, so we wouldn’t be getting any money to help with the server costs (which are really pricey). The PC costs are next to nothing outside of our daily operating costs, so it isn’t an issue for us to keep it running," they responded.
"If anyone has any complaints about getting points back/etc. they need to bring that up with THQ and not IllFonic – we don’t have any control over that kind of stuff. Nexuiz should be removed from the XBLA store soon (if it hasn’t already).”
As for buying the XBLA servers: "It certainly is a possibility. Unfortunately, at this time we just cannot justify the cost."
Nexuiz was built using Crytek's CryEngine 3 and released on Xbox 360, PS3 and PC.