I haven't read all the posts, but have read a decent number of them. Forgive me if I'm redundant.
I doubt they can sell 100,000 S/X per year if there isn't a 75D option. Anecdotally, it seems like the 75D is the most common S/X new delivery in my neck of the woods, and it is what I chose. For me, the extra ~80 miles of range wasn't worth $18k, and after 25,000 miles I have had two occasions in which the larger battery would have sped my trip up by ~30 minutes by not having to Supercharge. I would also disagree that the 75 buyers are going to just move to the 3. The S is simply larger than the 3 and the 3 is much, much smaller than the X. The 75D S/X is still a high margin car that contributes to their bottom line substantially, andI just don't see them walking away from that.
I think this is going to coincide with the SC v3 announcement that will let the 100kWh batteries in the S/X charge much faster. The 75kWh batteries wouldn't benefit from v3, so they can't offer it. I suspect they will produce 6-8 weeks of only 100kWh Model S/X and then come out with the standard range and long range S/X in the early spring with the 2170 cells. The SR will likely be an 85-90 kWh pack with 300 miles range and the LR will be a 120kWh with a 400 mile range. I suspect the pricing on the SR and LR will be marginally higher (3-5% maybe?) than how the 75 and 100 are priced now.
If this happens it will really put pressure on these "Tesla Killers" that are supposedly coming. The EQC, e-Tron, and iPace are going to look much less appealing than similarly priced a Model S/X with a range of 300 or 400 miles and significantly faster charging.