A very difficult issue I agree EKGO but the age of consent has been 16 since 1885 so rock stars shagging 15 year olds (or younger) have always known full well they were breaking the law.
So if someone says they saw X person having sex with a girl they knew was 15 in 1980, even if the girl herself consented, it presumably has to be investigated as it was and is a crime. The same if a girl believes she may have been taken advantage of. And so it should be - no matter how many cases there are, because that's the law.
However, given the costs involved and the burden of proof required I'd say the likliehood is they'll only be bringing cases against people that A) appear to have been prolific and/or B) targeted children and younger teenagers.
Edited: 16/11/2012 at 12:32