It would certainly be ideal to make 7.0 the start of a different "New Player Experience," but I feel like the only way that would work is if they also squish the levels down to a level 50 cap, with lvl 90s being lvl 45 at the start of the expansion. It would take a lot of "finagling" to get something like that done.

Also, more importantly, it'd cut into their story skip revenue.