I doubt they will open source AIX. I don't think they will see the benefits. Instead, open sourcing 50 odd projects that they don't really care about anymore or if there is a clear incentive to do so (such as community adoption to further the project) - makes more sense.
So would OS/2, but we all know that isn't going to happen.
AFAIK, IBM sold OS/2 a long time ago (it's now eComStation, owned by Serenity Systems).
Didn't they only license OS/2 to Serenity Systems? AFAIK the problem is that OS/2 still contains large portions of other corporations, such as Microsoft.
That's my understanding... they licensed OS/2 to Serenity, but IBM still technically owns it. But they can't open source it, since MS (and possibly others) own large parts of the copyright.
Even AIX on x86 was abandoned after a beta run many years ago. AIX and PPC are hand in hand and remain what they always were.