BA CityFlyer out of London City? 2 new aircraft arrivals expected in the next couple of months? Could an E170 work on that route? Complete speculation of course.....
Just to add to the points about Jet2, Eastern and BMIr, Jet2 are clearly not interested currently in city destinations and are flying headlong into the charter sector; BMIr are in a reasonable enough decline and have pulled plenty of routes and frequencies from LBA recently to suggest that a return with a London rotation is out of the question even though it is potentially do-able given the correct model; Eastern are concentrating expansion elsewhere and I do not believe LBA to be very high on their list of priorities.
I think if it is going to come from anywhere, it will be something altogether different rather than the "been there done that" airlines.