I think your question will not get any answer since A51 policy is to not discuss anything before the release (like Apple hehe)
Some questions that I think matters and must be answered though are:
1) Is AC3 a complete re-write or just another major upgrade?
2) Will the current modules work fine with AC3 or they will need to be changed in order to work with AC3?
3) Same as 2 but for patches, will at least most of the patches work?
4) Will the structure of already existing modules and features of AC3 be changed? If yes then themes for AC2 will not work properly for AC3 right?
I think at least these few questions should be answered so users and mostly 3rd party developers could know what to expect.
As you already know, we do not reveal any information till we have something to show you :))
The same goes for all the questions that Panos asked. We can only promise that all developers will have enough time to adjust their modules, patches and themes to new release of activeCollab till it hits the fully stable version.
Please be patient, and you'll find out everything soon enough :)
1. activeCollab 3 is not a complete rewrite of the system, but a major update to both framework and the product. PHP5.1 as system requirement lets us make a much cleaner platform to build on, so we are taking advantage of features it provides.
2. Conceptually, modules work the same way as they did in the past, but they will not work unchanged in v3 - you'll need to make a slight adjustments. For example, activeCollab 3 uses exceptions for error handling instead of returning error objects, so you'll need to alter code to use try ... catch. It's a pretty simple tweak though.
3. Themes will need to be update as well because we changed HTML in many places. Interface elements remain the same though - you still have a main menu, project tabs, bread crumbs, page actions etc.
4. We don't guarantee anything about patches. People will most probably need to dig back into the code, see if they can continue to work and update them.
As Ivana already said, we cannot discuss any details and you'll need to wait for the official announcement for that. Still, you should not feel discouraged about development for activeCollab 2.3 - most of the code will continue to work with just a few tweaks and we'll give more than enough time for developers to update it.
PS: This is what we can say at the moment. Because I know how discussion like this can evolved, I'll lock it now. At the moment I prefer to code, instead of discussing something that we haven't shipped yet ;)