HP would be my bet. They have "HP Cloud" which is OpenStack, and they're trying to get more into services in general.

OTOH, kind of a clusterfuck in general, and presumably if HP had any interest they would have just done the deal rather than this customer-terrifying announcement.

Maybe someone from Asia?

I would put my money on Cisco. They have been trying to reinvent themselves as a cloud company and clearly their financials show declining margins on hardware as the market shifts to cloud. Their intercloud announcement is interesting but not real yet and I think a Rackspace acquisition would give them a serious boost just as the SoftLayer acquisition by IBM has really accellerated IBM's move into cloud services.

The other possible buyer could be EMC -- for similar reasons -- but I would definitely think Cisco would be more likely.

Most likely to be private equity. IBM got SoftLayer after GI Partners rolled them up with a couple of other acquisitions.

Does Oracle still have whatever fragments remain of Sun's cloud service that nobody ever used?

Another possible option could be one of the big consulting firms - Accenture, Deloitte, CGI, etc.

Facebook has Parse, maybe if that demo matures to having RAX needs then it's worthwhile.

Parse was on AWS, at least before the acquisition, if I recall correctly.