Fabrication is a framework unto itself which utilizes PureMVC, but is managed by its own development team and grows at a pace that makes it difficult to fit into the way the rest of PureMVC.org is managed. In order to maintain a semblance of order on the site, (and because setting up all the permissions is a nightmare) I approve and tag releases and manage the wiki. This works for demos or utilities that rarely change, but makes me a bottleneck to progress on something as large as Fabrication.
And to answer your question; no, Fabrication will not be incorporated MultiCore and Pipes in the future. The goal with PureMVC in general is to have the framework be as small and simple as possible, bugfixed to maturity and left alone. It is extended with utilities (like Pipes). This keeps the framework from being a moving target under continuous development.
Don't you hate having to continuously upgrade software that already works because someone at the lab kept feeding the creepy feature creature? I know I do. Eventually software gets to a point where you're using 20% of the features and living with the 80% bloat that you're forced to accept to get those features.
Don't get me wrong, I'm not casting aspersions on Fabrication. It's just that there is an onion-skin hierarchy of developer needs to consider here:
MultiCore works. You can create a Flex Module (or Flash SWF) with its own Core, and just instantiate the thing in your application treating it like a custom view component. This just lets you have two PureMVC cores running without stepping on each other's toes. They don't even have to communicate with each other in any special way, you can just use events and expose methods.
You don't have to deal with Pipes unless you want them. Only once you find the need to communicate back and forth without having references and invoking methods or sending events do you even need to consider it.
MultiCore and Pipes work great together, (yes, I planned it that way
and you can plumb them easily in a short Command. If you only have 2 or 3 modules, this may be the easiest, most lightweight way to go.
However, if you've got 50 modules, dynamically created and destroyed at runtime with complex communication networks to establish between them, then you might desire a framework on top of MultiCore and Pipes to help with the plumbing. That's where Fabrication comes in. It has loads of helpful functionality for helping you do this easily, but if you don't have this level of need, then it's 72k added to your app that you could easily do without.