Right now, the one and only 4680 offering is the MYAWD with 279 miles of range and slightly slower acceleration. It is not meaningfully lighter than the existing MYLR.
All US MYLR are made at Fremont, and use 2170 cells with a rear mega-cast. They might start doing front mega-casts at some point - we have no idea if/when.
We would imagine that at some totally-unknown point, Austin will create a 4680 based MYLR with range comparable or slightly better than existing. Absolutely no one knows when that might happen, or how fast Fremont would follow Austin and go 4680 for MYLR. We don't really know why Austin punted and took 20% of the 4680 cells out to create a smaller pack. We don't know when supplies of 4680 would be high enough to support volume shipments of a "new" MYLR. We don't even know if they'd call the new thing a MYLR, or if it'd be a MYAWD+ or something else.
It would probably need a fresh EPA cert if it's a new pack, so we can be pretty sure it's not coming with in the next few months since there's no sightings of anything like that in the pipeline.
I'd love to see a ~340 mile 4680 MYLR. I'd guess it might happen later in 2023 timed to make it possible for Tesla to convert both their factories at about the same time. This is of course, a guess - Tesla does what they want.
My advice is order what you want, don't sweat the details. A 2170 MYLR is gonna be functionally almost indistinguishable from a future 4680 MYLR. The 4680 one is just cheaper to manufacture and assemble, helping Tesla be more profitable and make more total cars.