The health of prototypes - Grand Am DP's have only been getting around 12 per race at most regular events this year I believe. Add to this that ALMS has NEVER had a strong prototype field - its used to be around 2004 two outdated Dyson Lola's against the Champion Racing Audi R8, then when Porsche came in they effectively merged classes to give Audi some competition. Highcroft gave some competition when they came in, but was that not with a P2 car? Was it not a P2 car that De Ferran won the ALMS in? The prototypes have never been in good health, to be honest most of ALMS has never been in good health.
GT? Well GTS / GT1 was always a dying category and around 2004 was just Corvette vs the ACEMCO Saleen S7R, with Aston Martin's DBR9 chipping in sometime in the years afterwards. GTE (aka GT2) had been the best class and done well, with BMW, Porsche, Corvette, Aston Martin, Lotus, and now Dodge.
Point is the ALMS has always struggled, and the merger is good as Grand Am in all honesty has struggled a little in the Prototype respect.