I think people are missing the point here, just because Nintendo plans on supporting the Switch for more than 5-6 years doesn't mean there won't be hardware revisions in between just like the handhelds have gotten. Im pretty sure that Nvidia and Nintendo are working on the upgraded hardware as we speak and will probably be the main focal point for their Xavier chip coming out.
I think e3 2019 would be a great time to show this upgrade off!