my gut says:
* you will get a new Switch revision within 3 years. A release within 2 years would be far better for Nintendo. 3 years is too long to be stuck with this same hardware, I reckon (though Nintendo will release new colours of the current model, as usual).
* It will have battery life that's at least an hour longer
* It will have on-board storage that's at least twice the size
* It will have 'enhanced' performance due to the new chips - maybe like 3DS to New 3DS or DS to DSi
* It will have a proper kickstand with multiple angles and more stability
* attention will be given to this problem:
http://www.polygon.com/2017/2/27/14712498/nintendo-switch-joy-con-controller-wrist-strap
* attention will be given to this problem:
www.youtube.com/watch?v=SbG3F9RwlcY
* the dock & main unit will have less drab colours
* we may see 'portable only' or 'dock only' Switches in future - Nintendo's desire to save money knows no bounds, so a 'switchless' Switch is something I would expect to see after some years in the future. A 'portable only' Switch would be freed from the compromises of being a portable and a home unit & a 'dock-only' Switch would save Nintendo a lots of yen, all-the-while making Sony and Microsoft cry as people compare retail prices between the systems (a bit like the role the 2DS plays now to get people in the ecosystem). Nintendo will still be a distant third in home consoles. But the low cost will allow them to survive and possibly thrive. The Switch already has to be far cheaper to make than Sony and Microsoft's systems, so Nintendo has to be making a nice profit on the hardware already.
* nearly all the early feedback & niggling support issues they receive on this unit will get attention in revision 2.0 - and there will be far more games to choose from - and it will be cheaper. And there will be far more cheap accessories available from third-parties.
* the dock is crying out for exchangeable faceplates & so is the Switch in my opinion. Maybe we'll see this cash-cow return.
I would estimate that the sooner they release a refresh, the better for them. I bet there were lots of things the hardware engineers wanted to do but couldn't due to time constraints.