Well, Lonemagpie hasn't mentioned it, but the Best-Of-The-Lot black&white Rigg episodes have just turned up on freeview TV in the UK for the first time in 20-odd years, so it's worth a bounce in case anyone here is encountering them for the first time.
OT, I don't see a revival ever working: you [almost certainly] can't recreate Steed and Peel without Macnee and Rigg; you could just carry on the style - and then reinterprate that style - but you'd have to start out without Steed unless you rebooted and found an actor who could hit the ground running (Macnee took years to 'get' Steed into his final form), and so on.
You could maybe go back to the original idea of an ordinary-ish man who takes up fighting crime after crime hits him personally. But you probably couldn't call it The Avengers without a lawsuit from Marvel, and the Batman/DC lawyers might have a word as well...