That's an interesting question. I've talked about it with Pedro Rosa who works here at Microsoft Portugal and CardSpace has some beneficts, as in some way it can be used offline. In one hand, Internet is becoming ubiquitous targeting cellphones and PDAs nowadays, but on the other hand if I want to  store authentication information on a magnetic card, with OpenID it's impossible (for now) unless I have an Internet connection.

I believe for now OpenID is better but has some fails (as CardSpace also has) that in a near future will be corrected. But the real outcome will be decided by Google, Yahoo and Microsoft. I guess sooner or later Google and Yahoo will adopt OpenID. Microsoft is also helping out and making both systems compatible with each other (which I think is a great thing!). But the proper question is if Microsoft will continue to have dominant position in the OS market. If everyone has Windows Vista that has an awesome compatibility with CardSpace, why not use it?