Read through the posts on the Model SX line shut down. Seems to be an annual thing. The Model 3 and Y have multiple assembly lines and can be updated without shutting down production, so line refreshes affect the entire assembly system. That said, a lot of new tech has been deployed in 3&Y, so a lot of updates are possible without any model refresh. Those changes could increase range close to 500 miles without a battery or major design refresh. Changes beyond line updates and refresh of internals, like the heat pump, are possible as well. They have built a second or third high pressure casting machine and that could be for the S and possible X update. If the casting machine is being used for a model refresh, that would include 4680 batteries and likely significant body updates.
The odds to me of changes are:
Line refresh: 99%. They will definitely update the assembly line and improve production processes.
Significant internals refresh: 65%. Seems likely that the heat pump, wiring harness and other improvements will be deployed. This will improve the car and reduce assembly steps and factory floor space required.
Casting and body refresh: 20%. I think it’s early, plaid listed as available late 2021, so making the plaid body refresh before the plaid spec car seems unlikely. This would be exciting news though and mean the 4680 batteries would be in use already.
I agree with this analysis. I think the extended downtime (beyond typical S/X shutdown) will be used for some upgrades to the line / vehicles, but I think 4680s are unlikely at this point - though as you point out, not outside the realm of possibility.