If anything the Switch makes this less likely. Nintendo handhelds will always remain strong. The mobile model is not a substitute for dedicated handhelds (yet.) So Nintendo will dominate the dedicated handheld market with the Switch, and will just keep upgrading the system's abilities incrementally for the next five or six years. Basically they've made their own medium sized niche market, which was their goal for a while noe after the Wii/DS era. Neither the PS4/XBO nor the mobile landscape act as perfect substitutes for the Switch, and Nintendo gets to control their games/amiibos. Just face it, if you want to play Nintendo games either get the console or wait until the emulators work out their kinks half a decade later.