I would wait for another year because the major improvement that I am looking for is the new 4680 Cell batteries.
Also If the Model Y gets the air suspension, this I would also be another reason for getting a Model Y.
Unless you really need the hatchback, or to get a 7 seats,
there will be not so much dramatic changes with your Model 3,
except the inside be roomer and the trunk more practical.
You have already a Model S, so hatchback requirement is not really an issue, I guess.
Besides getting a new car, with some new improvements,
like the heat pump but this not really important in California,
there is not that much changes, except the improved space and higher door in/out access.
Your Model 3 has only 17,000 miles, so not really need to get a new car,
since the warranty is 8 years or 80,000 miles I believe,
and the tires can certainly last for a while.
Since you have FSD, I would recommend selling directly to a third party,
otherwise FSD will be disconnected by Tesla and you cannot monetize this option.
Those sites
FindMyElectric, CraigsList, eBay... could be some options,
but this takes time, and you have to meet people for a test drive
and trust that you will get paid, I guess you should get a cashier's check.
I noticed that you don't want to re-order FSD, at the time you bought your Model 3, FSD was like a $2k or $3k option,
but now a $10k for it is a big commitment, unless you want only getting a temporary subscription.
If you keep your Model 3, you will be able to see how FSD will be evolving when the Beta version will be available to everyone.
But you might have already FSD with your Model S ?
In California, the sales taxes are now 10.25%, that's a lot of money down the drain, that you already had also with the Model 3.
Getting a new Tesla and having to pay California sales taxes and FSD is like a 20% hurdle every time you change your car.
In conclusion, best is to drive the Model Y to compare it with the Model 3, may be you will find it too heavy or maybe you will like it better.
Since your Model 3 is in perfect condition, with low mileage, and if you don't really need a hatchback, I would prefer keeping the car
and put the money I would had spend for a new car, taxes, and FSD, to buy instead some $TSLA
and wait to see what new improvements (battery, suspension, FSD...) will occur next year.