Neither Sony or Nintendo will be making two distinct platforms ever again I don't think (as in console + separate handheld).

It's too cost and resource intensive to support two platforms anymore.

Handhelds used to have far more primitive technology but today handhelds can run even modern games like The Witcher 3 and soon will have chips that can easily run PS4/XB1 tier content, the iPad Pro released in 2018 already matches an XBox One S. And every year that tech gets better and better. 

This is not like 2004 where DS games ran at N64 level at best and games could be made by 15-25 people primarily.