Near as I can figure, (after having tried to dive deeply into this over the past few months) is that the next version is going to be OOP/Modular, using the idea of perl modules, and OO calling conventions.
The extent of this is not clear yet, without a good application (the setup.cgi is sort of minimal).
How will it overlay on the old links? In short, it won't.
You will import (upgrade) the database into the new table structure then pretty much start fresh.
DBSQL.pm is gone, the functionality seems to have been broken up across several core modules.
The program will have the same "functionality" of the old links, it will use templates (probably with a few changes, most notably in authentication) and then you'd "build" the site in the same way.
But, none of the mods will work. That means, a highly customized site will have to start to re-do the customizations.
The upside of that is most of them will be easier, some may already be built in.
The versions of the mods/customizations that are done may be better than the ones that are in the 1.11 version, etc.
Because the data is in a "database" the data is portable between versions.
The snapshot code right now is only the core/base modules.
Near as I can figure, the GT libraries are the "core" or "base" objects, that are used in all their programs. The "application" directory, such as "Links" or "GossamerMail" or "mysqlman" will have their own versions of the base class objects, and be linked in AHEAD of the base class. If the application overrides the base class, that will be used. If the application doesn't, then the base class will be.
Each set of core functionality is set into it's own module.
When new functionality is needed, either the module is expanded, a base class is upgraded into an application class, or a new module is created in the application directory (or core directory if it's generic).
So, Upgrades will _not_ be painless. But, creating a working site should be a fairly quick process of loading the new code, setting the defaults, then recompiling the site.
Hopefully before the final version is released we'll have an idea of what templates have to be reworked.
This is my take on it, but I probably don't see all the "features" yet.
To this end, I'm going to start several threads in the next few days on mod_perl/Apache/modules and try to get some head start on the logic process that will be involved. http://www.postcards.com