The B-29 will no doubt require a lot more detailing and modeling than the B-25s did.
Also, the poll simply determined that the B-29 would be moved up the list, but that's not to say that it's going to be started right now. They have other things in the pipeline. They're always working on minor updates and major ones (I wouldn't be surprised if we see 1 or 2 updates before the B-29, to add bits of code or do something that allows the B-29 to work at all).
I would expect nothing before July, rough guess.
C'mon folks, they're still working on updating the older 3D models, they just added the Betty, the Panther, they DO have other things in the queue!