I find it highly unlikely that 2k did not consider it when the annual steam sale came around.
I'm pretty sure they were already planning to include the X-COM bundle and UFO+TFTD in the steam-sale already but It's highly unlikely that they didn't consider the impacts of Xenonauts and OXC when they decided the %off.
It's difficult to say whether they increased, decreased, or stuck with the same price, but you can bet they thought about it at some point. I wouldn't be surprised if traditional X-COM has been pulling almost as much revenue as Enemy Within DLC lately.
In all fairness, 2k should pay ninex's bills for hosting the OXC team. We're doing a lot to redirect the attention of disgruntled hardcore fans and keep X-COM relevant. Of course that goes both ways but OXC isn't getting paid.