Yay Epic transmutes.
I'd be really really surprised if they go live with 4.3 given what Blizz has said so far about "Epics only available as raid drops" - I can see them adding the code into the patch to activate sometime later so that people don't have to d/l a new large patch every other month.
I'd bet on the recipes being introduced as vendors in the new raid instance, the same way that you could get patterns for boots etc from ICC entrance point vendors for . I'm guessing that the new JC cuts will only be available from new vendors in the new raid, and you'll need either a or a or new rare item XXX that drops only in the Deathwing Raids to get them and that transmute recipes will be active a while aafter 4.3 goes live.
I'd really love to see some actual craftable purple jewellery appear for JC. I'm still miffed that et al recipes were purple but items were blue .... That would keep people doing JC dailies as tokens would still hold some value as there'd be demand for new jewellery pieces that used CE's.
I do have some JC tokens stocked but will actually be a sad panda if you use them to purchase Epic Cuts. Will be interesting to see what happens to the cut rares market once 4.3 drops. Will everyone and their dog who is currently stockpiling tokens get rare cuts with them and swamp that rare market? Or will they just blow them on CE's.