I suggest people like the idea because they assume they’ll get new trains, probably orange ones, and Oyster PAYG with cheap fares, hopefully with their station in zone 6. Also there’ll be no delays, 100% reliability, 10 tph to Moorgate, etc etc.
The truth is obviously somewhat different...
Years ago, TfL taking over would have been great for a number of reasons that have happened anyway.
We have the new trains. We have contactless to WGC and Hertford on the inners. We have more trains (with more to come at weekends and then more trains in general come the new signalling).
TfL taking over now is more political than anything else. New livery but no other changes that I can think of.
Talk of LO taking over existed since 2006, and for a long time it was a no-no, then possible around the time of GTR taking over, then when GTR had the problems it did. But since then, things have improved and now TfL has no money.
So LO could be some way off, unless Grant Shapps is still transport secretary come the GTR contract expiry, and decides to make it happen so Brookmans Park can get 6, 8 or 24tph (in any case, I'm told he uses Potters Bar these days so probably doesn't care so much about Brookmans Park as he once did).
I swear I've read mention of a full rebuild of some sort down the line, hence the weird arrangements with platform 5's gateline(s) and the overbridge. Could be wrong, of course.
There are/were some grand plans for the area, but like everything (perhaps also like TfL taking over), things change. I believe there are plans going through for a major overhaul of the town centre, but the plans for the station, part of the leisure centre car park and rumours that even the theatre would get knocked down, as part of some massive new shopping centre/station/residential complex seems to have gone quiet as it relied on funding from multiple organisations.
Now with Brexit looming, we have to see how the economy fares. I suspect no more station work will happen until the plans are properly drawn up and approved/funded. It's good that NR funded the platform 5 works ahead of schedule, or else that may never have been done.