The Scottish services tend to run fast to York, so are of little use to people in Peterborough, Grantham, Newark, Retford etc.
There will still need to be services from London to these stations (possibly to Leeds, possibly to Hull or other northern destinations) which may mean more trains are able to stop at Stevenage/ Peterborough etc (rather than having to run non-stop to suit longer distance passengers.
Surely having more trains stopping at these southern ECML stations would be a good thing over-all? At the moment some places are being held back to try to squeeze in non-stop trains on that section of line.
Similarly it looks like Milton Keynes will get more trains stopping there.
That's partly correct, but not exactly. Take Axminster or Yeovil Junction as an analogy rather than a direct comparison (comprable with Retford or Newark) or Salisbury (comparable with Peterborough). Now, it's possible to argue that Axminster, Yeovil Junction and Salisbury have a
better service today than they did in the 1950s. It's better tailored to the needs of local people, runs to a 1tph even-interval timetable and is operated by modern DMUs. So what if you need to change trains at Exeter to reach anywhere west of there? You would normally have done that anyway, the
Atlantic Coast Express only barely served Axminster, although it did stop at Salisbury, and the
Devon Belle didn't stop there at all!
Just don't try telling that to the people who live there! Not that far to the north, Westbury and Castle Cary have an HST service which reaches Paddington far faster than their trains reach Waterloo. In fact, there are some times of day when it's quicker to travel to Westbury rather than wait for a Waterloo train, if you have the option. The relative pace of development on the Berks & Hants has been much higher, at least partly because of the diversion of long-distance traffic.
Now, I very much doubt they're going to cut services
that far. A worst-case scenario is 3tph semi-fast with minimal on-board facilities, along with cuts to stations and the possible closure of a few loops. I'd expect them to be operated by the shorter version of IEP. Stations will most probably see reductions in staffing and building closures, certainly a loss of catering. A better scenario would be 4tph including 1tph to Newcastle, giving a better link to HS2 for traffic northwards.
Milton Keynes (and Stevenage) will be affected too, but in a different way. Most likely, this means increased suburban frequencies and increased parking. What that will do to station facilities I couldn't even guess, since there may be more people, but they will spend less time there. That's closer to somewhere like Woking or Basingstoke.
So, the history of express traction out of King's Cross will be, the early GNR engines, Stirling singles, Ivatt Atlantics, Gresley Pacifics (with later Thompson and Peppercorn additions), Deltics (plus the odd 47), HSTs, 91s (and the odd addition), a few years of long-form IEP
and that's it. I've been lucky enough to be able to use the ECML throughout my life so far, as a fringe benefit, one of very few people who heads north, but does not live in London. I'm now aware I can't take that for granted.