It's the logical move, even if nothing official has ever been uncovered to suggest it is going to. Despite plenty of people talking about it in the industry, it could still all stem from a rumour/aspiration that has spread to become 'true' because so many people repeated it.
However, there's no other sensible move in my opinion. Making it part of the ICEC franchise is just plain dumb and if LO is to expand all over London, this is one of the obvious ones - given the important and very busy line into Moorgate.
Certainly the line to Hertford should go over to LO, which will be totally separate from the ECML (technically) when the new lines are opened. WGC might be a issue, but one I am sure can be solved.
An earlier poster suggested the semi-fast trains to London from Peterborough and Cambridge could go via the Hertford Loop, but given these call at WGC, Hatfield and Potters Bar, I am not sure that could work - although the timetables are going to be totally overhauled when the GN/TL lines join - so I guess that's the time to look at ideas like this.
Perhaps more trains can run semi-fast to WGC and turn, as they do in the peaks, although I'm not sure I want to suddenly find my 21-25 minute journey to KGX is slowed right down because of new stops at New Barnet, Oakleigh Park, New Southgate etc.