There is a benefit for Nintendo staying with AMD, a familiar GPU architecture. ARM is already ready, it has everything that it needed when the new consoles where being designed, meaning, x86 could have never been on a console again if they had started not much time ago.
The soonest a new Nintendo next gen console will come out is Q42016 and in 2015 we will see 64bit ARM everywhere, from standard cores to custom ones.
There is one "player" that could be a major advantage to Nintendo also, if they do decide to drop AMD, Imagination, PowerVR with ARM64 cores or with MIPS64 cores.
I wouldn't trust NV with a SoC for my own product ever, just look how the TK1 Denver is lacking so many OpenGL extensions on the Nexus 9 compared to the TK1 A15 on the Shield Tablet. Same GPU, less features, older driver on a product 4 months newer.