There is zero sense to release another completely different platform from Switch along side Switch, because Switch is also handheld in same time, and one of biggest advantage of Switch for Nintendo is that they are now working on games for just one platform. In some point Nintendo will just release Switch Mini/Pocket that will have more affordable price point.
Problem with this would be that the Joycons would become even smaller, and they are too small already for people without small hands. They could be fixed to that Switch mini - but wouldn't that defeat the Switching mechanic?
Hence why I think they will bring one handheld with fixed Joycons- which can be switched into a Smartphone. A smaller Switch would be in that territory anyway sizewise, so why not try and fuse the best of both worlds together? Nintendo could change a portion of the eShop into an appstore (because no android, hence no app store) to bring productivity apps as well as some smartphone games and make another Smartphone unnecessary if you have that kind of Switch phone = Multimillion seller guaranteed.
The Nintendo eShop rating Thread: http://gamrconnect.vgchartz.com/thread.php?id=237454
The Steam/GOG key gifting thread: https://gamrconnect.vgchartz.com/thread/242024/the-steamgog-key-gifting-thread/1/