My Personal Guess would be sometime between now, and the end of next month.This sounds amazing! I can't wait for the Direwolf20 pack and the "ultimate" pack (not that I won't play the FTB maps). Is there a rough ETA for the ultimate pack with all world gen for the foreseeable future included? I love to get a 1.4.5 survival map with all my world gen in. I have my own mod collection going, but a having a launcher and those standardized IDs are so tempting. I don't mean to be pushy and I'm sure you guys know not to rush the pack releases (and some things are out of your hands RedPower for example) and are going as fast as you can, but if you can give a vague estimate (when all world gen mods are ready, between now and 2020 etc) that would help me decide whether or not to use my own pack or wait for awesome FTB packs, if you can't I completely understand. Keep up the good work!
Now I'm unsure if this is still the case, But Last I heard they were waiting on Redpower to Update to 1.4.5, and IC2 to push out an update to fix some of the current (IMO, Major) Bugs in it. After they update, I would give them a week or two to prepare the pack (I mean, It prob won't take that long, but who knows?). But remember, this is my personal guess I came up from reading around the forum (and filling in some blanks myself).
Anyways, You could start a map now with your own pack just to screw around in, Test some of the new mods out and whatnot, So you know what your getting into when starting your "Real" world with FTB. Alternatively, you could start your "Real" world with the Magic Pack, and switch the map to use the Ultimate Pack when it comes out (May have to use a Myst world, or find new terrain for IC2 Rubber Trees and whatnot). You would have to live without IC2 and whatnot for a bit (As you wouldn't want to risk ID Conflicts when installing it yourself). As what I gathered from the Post you Quoted, The ID's should stay the same in both packs meaning it should be fairly simple (Though, and be prepared to restart just in case as things may change) to move over.