Some can be done without rebranding it as a new revision.
If they decided to go silent, not changing the shape o product or price, still would be nice to have the 4K output support (although is unlikely) and Better WiFi module would be a must (however, it wont solve the problem because you will still play with people with switches with the old WiFi).
But if they go with rebranding (switch pro, switch+, switch XL), with new shape, dock, pricing point, we could go bolder:
Sub 14nm chips to better efficiency, that would allow to reengineering the internal parts to not overheat when playing with dock clock in HH mode; more battery life (well, user could select between performance and battery). Yet, 1080p bigger screen, new kickstand, blutooth, more storage, better dock.
But if they go like this, I cannot see why not a mini switch/switch boy using the new chips. limit the clock to HH mode clock, attached controllers, portable dock/cable to streams to tv and done. A more HH friendly device and lower price point could reach new consumers, specially in japan.