GG's dropped a few hints on RideMonkey regarding the stays. Nothing regarding carbon stays, but the models that aren't currently for sale are getting very minor geo tweaks. (slightly longer CS for some models, slightly lower BB for some models, more readily available shock hardware sizing, Smash confirmed changing to 140mm travel to fit better between TP & Gnarvana). I inquired about when I can order MegaTrail stays, since they're still selling MegaTrails, and was told currently available bikes' seatstay kits will be available on the website Feb 1. No ETA on the rest of changes.
My personal speculation regarding those:
8x30 rear hardware
Smash BB down to maybe ~340
Shred Dogg CS to maybe ~426, BB down to maybe ~334
Trail Pistol CS to maybe ~430, BB down to maybe ~337
While I'd happily pay a few bucks more for carbon stays, I really doubt that they will go that way anytime soon, since it would add complexity (bonding metal inserts to carbon stays) and increase production time, rather than decrease it.
Most people run megatrails with 170 or 180mm forks, so I don’t see this happening. They’re not going to make the stays with 160mm when they do 155 or 165mm.I would buy longer CS for the Megatrail / Megasmash (bonus for 160mm rear travel in gravity to match the front 160 29ere). The ultimate would be a slightly lower BB as well but that might require to adjust head angle with headset or new cups.