IMO, all Tesla vehicles (so far) are pretty similar to each other.
On the one hand, Y is a less expensive X.
On the other hand, Y is a bigger 3 with a hatch back.
I'm not an expert in automotive consumer behavior, but I have to imagine that Y will cannibalize some amount of 3 sales. I also don't think that will matter that much - there is so much demand for Tesla vehicles that they are battery limited.
The Y is a crossover SUV like the X, but based off the Model 3 platform/chassis; what I'm really surprised by is the notion that they will build these in Fremont!
I actually interviewed at the Fremont Factory in '17 in logistics, the factory was a at Max capacity even with the low 3 numbers being produced. In 18-19 they hit their stride and started to use auxiliary lots:
https://teslamotorsclub.com/tmc/threads/found-a-lot-of-model...
They stated that at full capacity and with a successful ramp up 3 would overwhelm their storage capacity, so turn around was critical with little to margin for error; if anyone remembers all the Tesla employee parking lots were full and created a parking nightmare. Well, the outbound deliveries were equally bad. The shutdowns and refitting of the assembly lines showed just how drastic things were for a while.
They overcame this and I'm glad they did as they are now offering the 35k base model 3 as was announced in the beginning which was the 'game changer,' but I'm also glad I turned down the offer in the end, especially because they don't seem to be utilizing their Sparks and Shanghai factory for this model which would probably be best as S/X/3 are still being made in Fremont. Then again that stock price leap to 600 is pretty nice, just not worth the stress induced heart attack or stroke at 40.
I wonder where Semi/Roadster II/Cybertruck are being made then. I honestly thought they'd consider doing the Roadster II at Fremont for that extra 'Made in California' cache to match its price tag, but not the Y.
So if it will probably take some sales from both the 3 and X. But X sales aren't very significant compared to 3 sales anyway.