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I just don't think the Fusion idea works if the gap between the handheld and console is too large. It would require games to really be retooled so extensively to run that developers would basically have to make two versions of the game and the experience would be jarring going from one to the other.
PS4 quality games on a handheld, even with scaled down resolution is likely not realistic. Not for $199.99, not even in 2016.
I think even Wii U level graphics at 960x540 for a $200 handheld device with a decent screen is probably pushing things pretty hard.
Most likely Nintendo will choose an ARM core + mobile GPU, then simply take two of those (2x the CPU cores + 2x the GPU cores overclocked) and make the home console variant from that.
Maybe something around the Snapdragon 805 + Adreno GPU + 2GB RAM in horse power for the mobile, and double that for the home version.
Perhaps something like 300 GFLOPS for the handheld variant and 600-800 GFLOPS for the home variant (should be able to run a game like Mario Kart 8 comfortably at 1080P + AA).
