If it does support WebSockets than at some point in future we should be able to use w3.org/TR/2008/WD-html5-20080122 though right now it's in very, very sketchy draft page (look at the comments "Does anyone know enough about Bluetooth to write this section?" - lol)
In theory server-client WebSockets might work, though my knowledge of them is slightly too limited to implement real-time multiplayer with it, especially when it'd also require quite possibly short response times (all I did was some simple messaging component on a website with websockets).
@bolosaur - isn't PubNub a commercial solution? Considering that I'd most likely want to have my game as a one-time-purchase I don't think it's an option - in a long run such solution most likely would be unsustainable (especially considering a very limited amount of slots - I already can see a scenario when in first 2 days everyone rage because they can't connect, and in after a year I have to pay from my own pockets for a server because people buying game don't cover the maintenance costs).
For any solution to be worthwhile it needs to relay on self-hosted servers (or even better: P2P as much as possible with only one central tracker-type server).