Qatar can do underpasses / tunnels - and is even planning to do this
:
PHOTOS: More details emerge about Sharq Crossing project - Doha News
Sharq Crossing construction to commence in 2015 (Updated) - Doha News
Ultimate plans appear to be to close DIA and operate only from HIA - but there are transition phases that will last for an unstated period with only some airlines starting from HIA at end of April.
New April 30 soft launch date set for Hamad International Airport - Doha News
This confirmed by thinkofdolphins.
No publicly stated date for QR move as yet.
casablanca - yes that seems to be the present plan, as ground works appear to have started for the metro