Thought I would post an update to this thread because we now know exactly which concepts will be showing up at Pebble Beach. There is also some questioning as to whether or not the information is 100% correct though.
So the concepts that will be apparently showing up are the M4 GTS and 3.0 CSL Hommage concepts. The issue is that both of these concepts have already be seen at previous events -- The BMW M4 GTS as the 2015 MotoGP Safety Car, and the 3.0 CSL Hommage was seen earlier this year at the Concorso d'Eleganza.
That doesn't strike me as "brand new" so we will have to wait and see what exactly shows up.