I'm tending to think that Nintendo will just continue to iterate on the Switch hardware-wise from now on. Switch carts are just SD cards in a different case, which means that the current distribution form factor will remain viable for newer and larger games for decades to come as Moore's law continues to shrink flash memory (SD cards reaching half a terabyte are already on the market, and 1 terabyte cards are supposedly imminent within the next year or two).
I also tend to think that Nintendo is going to try and standardize on the NSO "streaming" approach to Virtual Console from now on, and will just keep adding new consoles on a yearly basis (to encourage people to re-up their yearly subscriptions) until they've made their entire back catalog available. By the time that's done in four or five years from now, Nintendo will have hopefully gotten their server game in order and people will just accept the ongoing yearly fee like we did with Xbox Live and PSN.
Regardless, I highly doubt there will ever be another case of a major platform change with Nintendo. It's just not going to be necessary anymore. The Switch's systems are the new standard, and the Switch game card, NSO's virtualization, Nintendo Accounts, etc. are all just going to be the standard going forward, and Nintendo will just introduce new Switch models with better hardware, basically like Apple has been doing with the iPad. Eventually they'll cut off the old models once they've gotten too old to run "modern" titles, and new games will only be usable on Switchs produced after x year.
It really seems like the logical step forward for Nintendo in the modern gaming market.