Hey gour - we'll keep the upgrade path in mind, definitely. There'll be an upgrade guide, and I've just been talking with Sam about a static code checker which you can run on your existing codebase and detect deprecated/removed APIs. That'll be something for a community project, most likely - but I think will help immensely with the upgrade process.
Thank you Ingo for encouragement. Let me tell you that in the meantime your book arrived here and is waiting on the shelf that I finish some post-migration tasks after moving from Linux to (Free)PC-BSD...then we'll start learning 2.4. ;)
Any traction on the static code checker for upgrading from 2.4 -> 3.0 ?
Primarily I'm interested in figuring out how to upgrade several dozen custom 2.4 templates/themes (framework and template language and in particular php code in /mysite/code) on a few sites that I have inherited.
Would be nice to do a test upgrade of the sites however there's a rather long list of error messages during my initial attempts at following the changelogs from 2.4 -> 3.x .