No, they are not coming out at the same time. The G4M1 will be in the next major update whereas the B-29 is, per the vote, being slotted into the next open development slot per Pyro's statement that there were several units in the queue already that will come first. What they are, how many and when they might be released is unknown. Rumor I hear, supposedly originating at the con, is that the Panther V G will be one of them, but having seen no supporting data I cannot give that high confidence.