I kinda doubt they're going with a DMP GPU this time. If it's not AMD providing the handheld's GPU, there are other possibilities in the mobile space (adreno, mali, etc) but the strongest contender I think would be Imagination Technologies' PowerVR. It was mentioned as a possibility, along with AMD, by Eurogamer in January 2015, a few months before Nintendo announced codename NX. However, EG learned that PowerVR and AMD as possible hardware providers 18 months earlier. AMD was no surprise, but PowerVR would've been. However PowerVR is in everything that powers iOS, from the original iPhone in 2007, all the way to the iPad Pro.
Here's that part from EG:
10/01/2015
http://www.eurogamer.net/articles/d...-next-gen-hardware-and-the-strategy-behind-it
PowerVR architecture has, since its inception in the mid 90s, excelled at being scalable. While platforms that use PowerVR have not always been successful (Dreamcast, VITA), it had seen major success elsewhere (NAOMI arcade boards, and especially in Apple and other mobile devices).