I've heard stories of it happening, so it's certainly possible.
I get the impression it depends on the locality. If a given town
has 1000 people in it with expired FIDs from 1998 or whenever it
changed, they're probably not going to bother all of those people,
but they might be more interested in harrassing current license
holders who just expired because the probability that they still have
guns may be higher. Who knows... the whole thing is kind of a
black box.
I've heard of one story personally (this guy I knew, a knucklehead,
didn't renew his FID, and the PD came and confiscated his
guns). Most of the other stories I hear are people that
get "raided" for statutory disqualifiers. EG, guy with an LTC gets
a DUI, gets convicted, and somehow the local PD finds out about
it and decides to pay the person a visit and then takes his guns, if
he still has any around.
-Mike