amok: I do not see this happening at all. I do see that there may be other steam bundles coming from them, but I do not see a total shut-down of cross-platform and DRM free bundles. Same as they now have other types of bundles (Andriod bundles, game jams and so on). I have no problems with these things co-existing next to each other.
Do not forget that this is also NOT a indie bundle... When HiB 7 comes it will be business as usual.
Kristian: Sure there will be other HIB bundles, but I am also certain there are companies out there who prior to this may have hesitantly allowed Humbe Bundle to ship DRM free, cross platform versions of some of their games in a HIB who will NOT be doing that now. I am also sure there are companies out there which GOG may have been able to persuade to sign on here which will not do so now.
Making a game DRM-free and cross-platform isn't something you decide on a whim. It's something you commit to from the beginning. If you decide later to do so, it costs a lot of time and money to fix, update, and test.
THQ is a AAA game creator. The games cost millions of dollars to produce and update. They're also a struggling company. Making their games cross-platform (and possibly DRM-free, as I don't know exactly the details about whether or not Steam has consolidated code for developers to use or whatever) would cost millions of dollars that they literally can't afford. There's no way, unless the games were already cross-platform, for THQ to make them so in their current situation.
Humble also happens to be by far the best-known bundle creator. They didn't choose to make the Humble THQ Bundle on a whim. The guys at Humble are also caring people, realizing that THQ needs help to keep afloat, and that they are probably the best option THQ has.
So either Humble rigidly adheres to the rules they have and the Humble THQ Bundle doesn't happen, or they make an exception to help a struggling company that delivers games everybody loves. I don't see why they would or should indiscriminately apply their rules to everybody in every situation, since every situation is different.