Maybe if we had new talents and new classes sure.People used the same arguments during the MoP Beta cycle. They claimed that there is no way possible that the MoP Beta could be a longer beta cycle than the Cata Beta because
(1) They don't have to redesign the old world, which is apparently what made Cata take so long
(2) They promised content would be released faster
(3) They couldn't possibly leave us in DS for more than 6 months given how boring and what a terrible raid it is.
Guess what? Despite all of that, the MoP Beta actually lasted LONGER than the Cata Beta did. The arguments are near carbon copies of the arguments people are making now for a faster expansion release and much shorter Beta cycle. I have yet to see a reasonable argument why history will suddenly reverse itself.
Any one expecting less than a 5 month Beta cycle is deluding themselves. History says it is more likely set to be a 7 month Beta cycle, so expecting 5-6 months is being optimistic. The window for a pre-July release to even be possible is quickly closing.