Originally Posted by
AdelaaR
Picking the next gear this way by computer would mean that most if not all of your gear changes would be both the front and the rear changing, which will make it impossible to keep power while changing and will make the changes longer to perform.
Bad idea.
One of the advantages of Di2 is that the front shifts are so good that it's easy to shift the front seemlessly under power.
Fairwheel bikes has already made a MTB with sequential Di2 shifting.
Single shifter sequential shifting is very likely to be an option on the next Di2 group.