SR-008 would make sense (the SR-Omega was really SR-6) but I do doubt that they will be releasing anything soon as the phones aren't the limiting factor in the Stax lineup, the crappy amps are.
The SR-007 Mk2/A has actually increased in price over the Mk1 as the Omega has had a MSRP of 180kYen since 1993 but this was increased to roughly 200kYen with the Mk2/A. There is little to no inflation in Japan so the prices are very stable, not like the blatant robbery in the rest of the world.