It looks like to me it's a two year wait for a Stern pin to have almost 100% code done.
If we go back two years - 2011 - (Rolling Stones, Tron and Transformers), these pins are complete. IMHO
2012 - AC/DC (almost done), X-Men (gah), Avengers (close?) - so 2014 should see these 3 done
2013 - Metallica and Star Trek. ST had a decent update recently, Met's should drop any day now?
As a hobby OP, I really only have one choice in the game for NiB, Stern Pro's. Everyone else has priced me out.
It seems like the only game Stern has abandoned is WoF.