I don't think you'll find too many parts shared between the sedans and crossover vehicles and the cybertruck. it is not necessary that one shares components everywhere. Some cars can be different entirely if need be. there will always be a market for the S and for the x, never very big, but that doesn't really matter. As long as they're a profit center they pay for themselves so it doesn't matter if they make a ton of profit or not. As long as they help Tesla's overall goal, they'll keep making them.
All other car manufacturers share as many parts as possible between cars. If you get into any GM car for a given year, you will find the same switches and buttons. Take the car apart and you will find some parts shared between the cheapest and most expensive cars in the line up. Subaru is so aggressive with this it's sometimes impossible to tell the cars apart from the interior even if you know Subarus well.
The more a company buys of a given part, the lower the cost of each part. Reusing parts already in another car also saves on engineering costs. Just to change the design of a single button requires engineering drawing be produced, and engineer to ensure it fits where it is supposed to, and then sending out to get new plastic molds made for that one part. When something is mass produced, plastic molds are cheap per part, but for low volume production it's far more cost effective to do something like 3D printing because of the cost of producing a mold.
Plastic molds haven't been made in the US for over 40 years because they need to be made of very hard alloys which can have toxic metals in them, then the slab of metal needs to be cut with precision lathes with very expensive bits to make the shape. The cost of the molds needs to be spread out over production of the part. If the company is making millions of them, the cost per part for the mold might be less than $0.01 a part, but for low production, the part might cost $10 a part to pay off the mold.
For something that doesn't need to look great, molds can be made from cheaper, softer metals and cost a lot less, but they will wear out quickly. That's unacceptable for a low volume production car that is presumably going to be expensive.
The refresh Model S was a big deal among Tesla enthusiasts, but I was watching what they did very closely. About 90% of the refresh was just merging new features from the Model X into the Model S line. One thing that is rumored to be coming with the S and X next year is the cabin camera from the 3/Y. Tesla may advertise this as a new feature and there may be a corporate customer who wants to buy S or X autonomous taxis who want it, but it could also be happening because Tesla wants to standardize more of the mirror/camera assemblies across the different cars.
There has been zero mention of any workers needing new training. Again people are reading way too much into this. Every single auto manufacturer does an annual 1-2 week shutdown every single year simply for maintenance, Ford shuts down all 9 plants every summer. This is nothing abnormal or indicative of a major refresh. Retools for a full production line refresh are typically 4-5 weeks. Tesla has been know to put profits before worker safety, so they have bucked the trend and refused to shut down for maintenance, but that can only last for so long until your hand is forced.
I said much the same when the refresh rumors started over the shutdown, but few believed me. The S and X lines have been up and running long enough some parts of the production lines might be reaching end of life and need to be replaced. Machines wear out.
Another clue in my thinking of of a refreshed X is that the delay of the 7 seater model Y may be related to the refresh of the model X. It could be the refreshed X was suppose to be out by now and they've delayed the 7 seater Y because they don't want to take sales away from people who would rather have the (more expensive) refreshed X. After the refreshed model X is released, soon after, they'll introduce the 7 seater model Y.
Personally I think the two are separate. Tesla may be seeing low demand for the 7 seater Y and high demand for the 5 seater, so they are focused on meeting demand for the higher volume car. They dropped the jump seats in the Model S because demand was too low to justify them remaining an option. The X being a much larger car can fit adults or teenage children in the last row. The last row for the Y is probably not going to be very useful except for small children and they will probably outgrow the seats in a few years. If you get the two row Model Y you get an extra storage space under the floor that you lose with the third row.