You´d better ask them instead of us, usually they run a batch every third month or so i think - but that depends on the number of pre-orders possibly?
From their website:
“You can still place an order to guarantee one from the next batch. We currently cannot offer a firm date on delivery, though we expect this to be within a few months’ time (from July 9th, 2018).”
You can always subscribe to their mailing list and so get notified when new units arrive, or you can pre-order to make sure you get yours as soon as possible. I would do that i i were you! And also maybe on a regular basis throw them a mail and ask about next batch - but not too often, you don´t want to annoy these hard-working gentlemen!
From my experience they are good at communicating with customers, especially would-be, they won´t forget you.
A guess would be next batch coming in 1½ months maybe? I don´t have anything to base that guess on though.