Peter has never fully gone away. I know a few teens called Peter and a 6 year old. Peter Rabbit is very popular again so I think this could actually return to the top 100 again soon. Peter doesn't feel anywhere near as dated as the rest.
John, Paul, Mark and Richard are all very classic too so I'm sure they'll make a big return in the next 20 years or so. When our own children wish to honour their grandparents I imagine. I actually know 3 Richards of Primary age but they're all Eastern European. It seems to be very popular still in that part of the world.
Names of a similar style which I can see returning big time one day are Steven, Robert, Christopher, Matthew Andrew, David (another which is still very popular on the continent - I know lots of young Davids from Eastern Europe).
Gary, Nigel and Grant on the other hand are far less classic and therefore less likely to return big style (was Grant ever that popular to begin with?). They definitely belong in the past imo!
I would put Ian, Lee, Jason, Dean, Darren etc in the same category as Gary and Grant. Don't feel classic enough to return big time but could filter back a bit when those relatives are old enough to be honoured.
Nigel is more fuddy duddy. Similar to Brian, Barry, Norman, Colin etc. I hope these names never come back!