Update: After writing but prior to publication, Nintendo has officially announced the next Nintendo Direct broadcast, which will air on the 23rd of September.
Nintendo is gearing up to reveal and release a new Switch controller variant, if patent documents are to be believed. Spotted by eagle eyed fans on the FCC website, the filing was completed on the 16th but only recently made the rounds. By all estimates, we should get an official look real soon.
Very few details are public at this point, so we have no clue about the design, layout, size or any other specifications other than some frequencies, which are what made it clear that the new device will be used for the Switch - the console is not outright named in any of the documents so far.
Even so, fans have speculated that Nintendo won't wait to do a reveal for long - we might be getting the official announcement of this new peripheral this week. The main reason is that patent info like this is likely going to be expanded with further documentation which would end up spoiling details and possibly even the design.
Additionally, fans have been expecting a September Nintendo Direct broadcast, with rumors having already made the rounds a while ago. While there are no guarantees, it would make sense to see a broadcast happen soon - it's been some time since the last one.
Rumors and leaks thus far have only spoken about games, including a new title in the Xeno series of games, which was the first first-party hint at a September broadcast after a number of unverified reports. These patent documents were our first hint at anything happening on the hardware side of things, what with the Switch OLED being a known update to the console - nobody really expected anything else in this segment.
Either way, we'll have to wait and see - it being Wednesday does not leave much of the week left for this reveal!