Here are my general thoughts on it at the moment, including announcement:
Announcement is probably incredibly soon. It's difficult to avoid extensive leaks when in full scale assembly, and assembling any later than this month means sitting on finished silicon for upwards of a year, which is expensive and a huge opportunity cost. Formfactor is probably nearly identical to OLED Model with the kickstand hinges moved to the top of the device to allow for more internal space, and a long, wraparound style kickstand with intakes at top and bottom of the kickstand indent on the bottom end of the device. Faster Game Card loading for supported games. 128-256GB UFS storage. Possibly UFS card, seems likely what with Orin boards using them. UFS card slot under kickstand. Black Joy-Con. No other visual changes; even the same logo on the back of the console, with "Super Nintendo Switch" reserved for the box and marketing. Black Dock with LAN Port to differentiate it from the white dock of OLED Model. Crimson and black colour scheme for marketing, otherwise using standard Switch colours. I expect it to launch pretty much imminently. Like, Switch final assembly began November 2016, launched early March. This thing might be in assembly right now (why else would Zelda OLEDs be ready so ahead of time), so, late April to early May launch. Elden Ring, TOTK, Pikmin 4 launch window games with 4K patches for most of Nintendo's popular evergreen titles.