As for when, eventually is as good an estimate as any.
IF they've straightened things out between the various manufacturers, then batch 2 can start as soon as batch 1 is out the door, but the bulk of the parts that are being produced now will go to produce the rest of the first pre-order group. I believe.
If I remember right, they'll need 3k more cases for the rest of pre-order group 2, they'll definitely need more boards, but they may have enough nubs as I'm guessing they'll order as many of those as they need and the nub company can seem to produce them in crazy numbers once the testing is completed.
ED, Craig, or anybody from the team feel free to correct this if I've missed something.
Edit: in theory batch 2 shouldn't take nearly as long to fill as batch 1 as most of the kinks have been worked out. Board revisions are done. Banks shouldn't reject funds anymore. Hopefully another nub company doesn't go down the drink. The case issues seem to be largely resolved. They've worked out the assembly line for Craig's place - the things that worked, and the things that needed to be tweaked.
The biggest question, and probably the one not even the team can answer, is how responsive the component manufacturers will be to future orders of parts. If they get all but X part in a timely fashion, you still don't have a Pandora. X can be the cases, nubs, LCD cable, LCDs - though this doesn't seem to have been an issue, or boards.
The nubs seem to have been resolved.
I know they've talked about a different board manufacturer if that turns out to be a hang up, and if they HAD to they could move the case manufacturing to the U.K., and the Chinese holidays are coming up which may slow things down a bit, so we'll see. From the latest updates it seems like at least with this batch of parts things are "in line". We'll see if that holds for the next batch to finish up Pre-Order group 2.