I looked at the total downloads for all the templates that are still for ONLY Joomla! 1.5. A massive total of about 82 templates (there may be a little bit more as I did not find data on some of them, maybe 3 or 5 old ones).
I checked the total downloads for all of them, and wherever there was data, I ranked them accordingly - from 1 to 12 with the Highest number of downloads first. See images.
I ordered them per year, hoping this will help in finding out quickly how to prioritize. (Nothing genius). This was checked on 31st January 2012 between 15:07 to 15:30 GMT.
Most (if not all) of the 2010 and all of 2011 templates are already on Joomla! 1.7 with the latest framework, I presume. So this is based on ONLY 1.5 templates running on the old framework.
Will there be upgrades from 1.5 to 2.5 or will we need to redesign from scratch. We stayed with 1.5 instead of upgrading to 1.6 or 1.7 as originally there was to be upgrades to 1.8 available. Going to be a busy month if we have to start over on all our sites.
And thank you for all the efforts the team has made with all the changes. I understand the workload you face as a result of supporting all these version changes.
Correct me if I am wrong but a few months ago there were posts regarding the migration or roadmap that Joomlart was working on. All templates were going to be updated, to use the JAT3 system and they are not. Also mentioned going from 1. 5 to 1.8 as an option since a lot of 3rd party development skipped 1.6 altogether. That's why we stuck with 1.5.
Given that the process of going from 1.5 to 2.5 now looks like it involves upgrading to 1.7, I think there will be many issues to sort through. It's not just the template but the the extensions and the modifications.
We have clients asking about the upgrade process and I'll assume it's better to start over as the 2.5 templates are introduced rather than try to upgrade unless there is a script to do so. How that would work with 3rd party extensions is yet another issue we all face. K2 and a few other components are built into the recent templates releases and I don't see how upgrading can be a simple process. Correct me if I am wrong.
We do have plans to upgrade templates from 1.5 to 2.5 in the coming time, however, a confirmed date / month for the releases can not be provided at this time... we have been pretty occupied on other important projects.
Plus Joomla 3.0 with twitter bootstrap and other changes are bound to affect the templates, so we are waiting for 3.0 too.. coz it would be lot of work for us to redo all our current templates too...
Too many joomla versions and too many core changes makes it harder for us to be in sync... too many backlogs to take care of.
We shall announce on the blog, once we can have a clear roadmap for release.