Raven on 22 March 2019
I have a hard time believing Nintendo would risk resetting their userbase even when the Switch 2 finally releases. Rumors suggest the next Xbox and PS consoles will be BC with the current gen, so Nintendo forcing everyone to restart would just be a sore spot for marketing.
But as for the OP specifically, I seriously doubt it would be a brand new system that breaks compatibility with the Switch if it's called the "Switch Pro". That would be super confusing, and be unlike any other mid-gen upgrade that they've released previously (Game Boy Color, DSi, New 3DS).
