First off, when I was at ZendCon back in October, there were already hosts providing 7.0 RCs. Just like every other version that has come out, if your host doesn't provide it by the first patch version then you should switch hosts 😛
Second, from my experience I can expect many shared hosts to upgrade much quicker than with 4 to 5. This is for 2 main reasons: A) the performance improvement means hosting more customers on less servers and 😎 its a much less painful upgrade for users than previous major versions. AFAIK it is a very easy path to upgrade, if you're not using new features AND your code worked on 5.6 in strict mode THEN you should be good to go to upgrade (IE I now have 7 projects running on 7.0 in production, and only 1 needed any code change at all).
Third, LTS distros usually back port security fixes into their provided version of software even after the software maintainers themselves say its not longer supported. So as long as your version of Ubuntu continues to be under LTS, and you continue to keep the php package up to date you should be fine. In the past, the core team has helped with security fixes for LTS distros even after EOL due to high potential for abuse.
As for the RFC to extend support for 5.6 - its current voting options are a) don't extend, b) extend active support to 1 year from 7.0 release date, with 1 year of security support following or c) extend active support to 1 year from 7.0 release date with 2 years of security support. Which really means, there is 2 options to extend active support for an extra 4 months, and 1 option to give an extra year of security. That's not a big extension - and my understanding following internals it its likely to be option B that wins out.