I was as Benno-007 visitor of the online summit and read the mailing list. Official in 2-3 weeks soonest but I think it could take longer, too. But 15.04, 15.10 won't come soon because of snappy testing. If you are experienced and don't need some main scopes (and apps like here maps) you can flash it yourself and at your own risk with ubuntu-device-flash, for example like this:
ubuntu-device-flash -v touch --channel=ubuntu-touch/vivid-proposed
And back to the old stable release:
ubuntu-device-flash -v touch --channel=ubuntu-touch/ubuntu-rtm/14.09
In this form this would normally not destroy all your data which is on a separate data partition. But you have to make backups or maybe you risk your data because of errors or problems.
If you don't know how to do all this in detail maybe you are not experienced enough and be carefull what you are doing or not. It's only a hint for some a little bit experienced people because it doesn't take long that this is official and stable without flashing on your own. I don't want to recommend it because maybe you want the stable version with all scopes, don't to damage your device for some reason and so on.
Greetings, lgd