Pahimar has considered doing it for a while, since he constantly gets requests for it. But as far as I am aware he hasn't shared any details with the public... at least not in written form. He may have mentioned something on someone else's stream. Your best bet is probably waiting until it actually gets released.
Besides, there's not really any secret sauce to it. Building your modpacks with the 1.6.x vanilla launcher is extremely easy, and you can see what mods Forgecraft 2 runs just by watching the various streams and let's plays. You won't be getting any dev versions of mods anyway. If it's not released by the author, you can bet that it won't be put into any modpack, Forgecraft or not.
I'm actually expecting it to be very similar to the current Unleashed pack, ported to 1.6, with some fluff cut out and a whole lot of iChun products added in. Maybe not Trail Mix but certainly most others
