Really nobody left, RAX is too big and requires another public company, mainly a blue blood to acquire them. IBM got Softlayer. Google, Amazon, and Microsoft obviously have their own clouds. RedHat has its own PaaS OpenShift. Awkward spot really. Perhaps Facebook wants to join the cloud hosting business, but I doubt it, since they've just coughed up insane amounts of cash with Oculus and whatsapp.
Smart play though, Morgan Stanley will figure out the details and likely find a buyer eventually. MS is kind of like `The Wolf` from Pulp Fiction or Mike Ehrmantraut from Breaking Bad, no questions asked problem solvers.
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.
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.
Smart play though, Morgan Stanley will figure out the details and likely find a buyer eventually. MS is kind of like `The Wolf` from Pulp Fiction or Mike Ehrmantraut from Breaking Bad, no questions asked problem solvers.