Very unlikely to be speeded up in my humble opinion.
Obstacles on the eastern section...
Single track through Grantham platform 4, and a low 20mph linespeed (I think, its 15+ years since I signed it!). Eastbound services are times to follow the westbound service through that section. If you swap them around and reduce the dwell times at Nottingham you are then importing a risk to the ECML as the westbound service would have to wait on the ECML for the eastbound service.
Central Trains looked at this before as the idea was to swap the paths over, alternate a stop at Ely one way and via the west curve the other way and save 1 unit overall. Even Central Trains rejected that as it was unrealistic on a day to day basis.
Nearly all services are booked slow line from Stoke to Peterborough on the ECML (max 80mph). Given the desire to run 8 LDHS trains an hour on the ECML you would probably struggle to get a 90 mph service to fit in (100mph when all the 170s arrive).
Eastbound crosses over the ECML at 15 mph at bith Grantham and Peterborough so it has to fit in between much faster (115mph I think) ECML services there.
Peterborough to Ely generally sees the EMR service a few minutes behind a Felixstowe liner across Ely Junction, and westbound they are a few minutes in front of the Birmingham-Stansted at Ely North Junction, and a few minutes ahead of the Kings Cross-Kings Lynn departing from Ely, with the Ipswich-Peterborough stopper right behind the Lynn. Given the increase in liners to/from Felixstowe it is common for the the EMR services to get delayed following them across the fens. (1L10 today, 27th, lost 14 minutes following 4L85) for example.
I'm sure others can summarise similar issues on the western section...