3 terminals with capacity for 55 million really?
It wouldn't be pleasent, but, potentially, yes.
There are plenty of quiet periods at MAN, just look at T2 on some afternoons, not unusual to see 1 or no aircraft on stand. Also, natural progression to larger aircraft will help.
So, yes, 55 million is possible. Are they at times airlines want to operate? Probably not. Will the terminal experience be comfortable in its current set up? Hell no.