According to the Ubuntu press release FAQ, they are pushing for a device to be released this year. If that I so, then I vote for ubuntu.

However, it is hard to choose between them all...

Ubuntu have the OS and can make use of the existing applications from the ARM Debian repos, but have no hardware announcements ATM.

Jolla are the spiritual cousin to maemo and can make advantage of the ACL but like Ubuntu they have no hardware announcements.

Tizen, well not a lot of people know much about this. Apps are few and appears reliant on HTML5 but Samsung already have the hardware on the market and are kicking out some fantastic devices.

A safer choice would be RIM as they are already building on both an existing "eco-system" (blugh), are following a more natural hardware progression path and if crackberry is any indication... Queuing customers.

But where's teh fun in being safe