Now you have 2 aftermarket oil filter companies essentially - M&H and First Brands, with whomever makes the microguard/ecoguard/Parts+ for OReilly/Federated/Same name coming up a distant third.
My guess is the fight for the private label business is forthcoming, or going on now. Once the two "bigs" get their manufacturing consolidated they will be looking for ways to make as many filters as possible. This was the reason Ford and GM helped bail out Chrysler in the 80's - they didn't want to compete head to head - margins go in the toilet.
Unless some others decide they want to play. You have Denso, Mahle and Hengst that could probably play there if they wanted to.