They could make a PS4 clone if they wanted, but it would not be as successful as the Nintendo Switch.
Nintendo has chosen to pioneer hybrid gaming, consolidating and streamlining development costs (time, money, manpower) of home console and handheld console into one, while gaining very healthy profit margins (far more than it did with Wii U and 3DS).
They are diversifying with iOS and Android games, theme parks, movies, amiibos, merchandise, etc. to buffer the slower years that may happen when only doing 1 console instead of 2 and they are well set for the future.
For some people, Nintendo Switch has made gaming on a TV obsolete or a side option.
So, it will be curious where the market finds equilibrium with this (as much technology use is focusing more and more on on-the-go use rather than less).
Maybe each market niche is steady for many more console generations, maybe traditional consoles end up with too small of a user base to justify developing a larger budget demanding successor, maybe something new makes it all obsolete.
Many possible outcomes... but as far as current trajectories I think Nintendo making a PS4 clone is a much less than 1% probability.
