These things are never a "merger of equals". Based on the relative position of each, it looks to me like Don Panoz is folding his tent. Possibly because of the politics with the ACO, but also because in the US, there just isn't enough of a fan base to support two distinct sports car racing sanctioning bodies.
I'm pretty sure we won't see a LMDP class, but that the current classes will run in parallel for a year, then everything ALMS will fold into GrandAm.
It's a pity, really.
OTOH, now is the time to agitate for the SLC or the new Franillac to be eligible for whatever prototype class gets defined!
This is from the ALMS site. If you read #5 it looks like they do not plan on running cars that would not also qualify for racing in the 24hrs of Lemans.
Scott Atherton the ALMS CEO is a former NASCAR guy. It will be interesting to watch how it comes together and how classes are broken out and whether or not DP's will be able to run at LeMans and in what class.