My cent: the huge discount recently granted on MS is a clear sign that something "major" is going to happen.
Those discounts happened in the past: remember when they were on the point to sell the MS Refresh two years ago?.
Thus, excluding that discounts are in relation to minor refresh, I "dream" that they are doing something on the batteries. Not necessarily 4680 (which probably require some important hardware changes), but a chemical improvement of existing format.
If I am not mistaken, Panasonic said that they were able to improve their cells density by 5% per year. Considering that the gross capacity of today's MS is still the one available in 2017 (or 2018?), a 20-30% increase is definitively possible, if Tesla decides to have it.
Elon is confusing on this point: in 2020 he pushed the idea of a MS having 600 miles range (MSplaid+). Than it was cancelled.
Changing his mind, he declared that 400 miles range are more than enough.
Maybe he is changing position again, under the pressure of competitors.
Lucid a part, we see NIO and Zeekr marketing vehicles comparable to MS with 140/150 kWh battery.
Stellantis has now announced a Peugeot 3008 with 435 miles range and 98 kWh battery, which will be built on the "Medium STLA platform".
This makes it credible that the "Large STLA platform" will really maintain the 500 miles range promise - soon.
A Model S with the same weight but 130 kWh battery would stop competition, considering the other advantages of the "tesla environment"...