In the filing, I believe, it stated that THQ still owns the rights to their backlog i.e. games already released. I wouldn't worry about it too much; however, there has been problems in the past with games being pulled from digital distribution like the midway games being pulled from XBLA when they went under. So who knows.
I'm assuming that nowadays they have it built into the paperwork to account for just this issue, likely a problem with Midway because it wasn't specified and defaulted to being taken down.
Very true. I don't know the licensing that was made with say, Valve, with the digital distribution and the event the license for the product was sold. However, considering THQ was able to keep their licenses for backlogs (still trying to find the source of this again) I doubt anything is going to matter. In the case with Midway, my guess would be they didn't keep their license for already sold games or your good point on the license never covered the specific event of licensing changing hands.