But there are some major infrastructure changes happening over the next few years. The improvements to the GN&GE joint line being the main one (including a flyover at Peterborough) to get freight trains off the two track section of the ECML from south of Grantham to Doncaster.
I also suspect that the IEP trains themselves will increase line capacity, as they'll have better acceleration than the HSTs and 225 sets, due to having distributed traction motors, so are better at recovering speed from station stops and speed restrictions . The class 180 sets used by the ECML open access operators certainly seem to have much better acceleration - I remember being on a Hull Trains service a few years back that ran non-stop from Kings Cross to Grantham in 55 minutes