UPDATE - According to prior certification listings, it seems HAT-001 might be the model number for the already-existing SDEV devkit, not an indicator of a Switch revision in development. Thanks to Mariostarn for the heads up!
Everyone knows Nintendo loves to revise their portable systems. Usually they revamp their portables with new colors and features as the years roll on. Could we see the same thing happen with the Switch? Some think a registration filed by Nintendo points to that happening down the road.
Just today, Nintendo has registered "HAT-001". What the hell does that mean? Let's take a look at some other filings to see what they mean.
Nintendo registered HAT-002 a long time ago, which is the portable development version of the Switch that resembles the design we currently have. Typically Nintendo uses 001 to signify a consumer console, as was used for DS, 3DS and Wii U. The current retail version of the Switch is HAC-001, and the cradle is HAC-007.
In other words, the registering of HAT-001 could indicate some sort of revision for the Switch set to release to the public. There are certainly things in Nintendo's past that would point to that happening, but this is all just speculation for now.
Also worth mentioning, Nintendo registered HAT-003 as well. This is the cradle development version of the Switch.