Sure, we'll get a third-party joycon with a turbo button and an analog stick that busts after three weeks.

 

I have no idea what goes at this point, however I would not be surprised to see Nintendo take a leaf out of MS' playbook and block off unofficial offerings via a chip. This would then mean third parties could exist but either for hacked consoles (something I am not sure I have ever seen for a controller), should the chips be suitably reverse engineered, those deemed OK by Nintendo, those piggybacking off an existing controller (see all those adapters that see you have to plug a controller in anyway) or that take official controllers, take them apart and build on top of that a la the Evil Controllers.

Hopefully I am wrong and people are able to make their own like the wii or something but that might be more optimistic than I care to be at this point.