I think it's too early to tell what will go and what will stay. Not withstanding LMP1.
The thing to keep in mind is ALMS GT cars are at the heart of the merger and will not see any significant change. Those cars are need to retain the tie to the ACO and the 24 Hours of Le Mans. So... consider everything else will align, from a performance standpoint, to the ALMS GT cars. That's the starting point and everything will need to "fit" around those cars.
That means Prototypes will have to be faster than GT and any other classes will need to be slower.
The Daytona Prototypes, while carrying more speed, can not get out of their own way in the corners. They are going to need aero help and bigger brakes. You really can't put more horsepower in them. The ALMS P2 car is far superior technologically and will out run the DP on most North American circuits. Finding the balance between these cars is going to be a challenge.... and probably painful ($$) for the DP teams.
Many argue that since there are more DP teams compared to ALMS P2 teams, that the P2 should have to adapt or go away. I wouldn't count on it. I say that given a fairly simple set of logical criteria.
It's not secret that the ALMS is by far a better and more professional show. For a North American series to survive, the racing format has to be inviting to teams from the LMS and WEC. Those teams want to race in the 24 Hours of Daytona, Sebring 12 Hour and Petit Le Mans. USCR will need a rules package that's adaptable to global racing.
However, to my mind, the most glaring rationale is this. If Jim France (Grand Am) wanted the Daytona Prototype to be the flagship class, why on earth would he even merge? He already has a series where the DP is flagship class. It isn't working. It doesn't attract manufacturers and it doesn't have global appeal.
Just my opinion... I could be wrong.
Sorry for the thread drift... nice photos.