It appears that the proposal to divert the Gogar Burn around the other side of the airfield has been dropped. This has presumably limited the scope for development of the aprons, taxiway and terminal.
The proposed arrangement does not create the expected unification of the main apron with the southeast apron. As a result, and unless it is remedied, the PCN of Taxiway Mike remains an impediment to regular long-haul wide-body operations from the large stands on the southeast apron. The illustration shows that the largest of these stands, stand 17 (the one with the LH 747), is adjacent to the elevated corridor and as a result has no gate lounge and no jetway.
I wonder whether the development plans will include extending the length of stands 6-10 by moving Taxiway Foxtrot closer to Taxiway Alpha. This could enable several widebody stands to be created, all with jetways, and gets around the PCN issue with Taxiway Mike. It would also provide a better opportunity to create gate lounges for long-haul.