Most likely yes. But Valve could make an agreement with Sony about releasing to X360.  If they're bought by Sony they're PART of Sony. That's what buying a company means. And what company makes games for its rival's consoles?  Microsoft also makes applications for Mac (Office, anyone?  ). It's very unlikely. But I guess it's going to be phased out in that case. For example, only total new games not to X360.