I dont think it is about the GR86. First off, the pictures of the logos could be a stock image with absolutely no meaning behind it. Second, it makes n sense that it will be the GR86. The two companies already settles to GR86/BRZ formula. Yes Toyota president told GR to make it different from the BRZ, but why would they reach out to subaru to help them do it? Yes subaru will manufacture it, but based on the advertisement, they will be making a car that will benefit both companies. Subaru helping toyota make a better 86 so toyota can take the sells away from the BRZ makes no sense.
I think this could be the GR corolla, or a FW revival. Subaru is long due for a performance hatchback and toyota wants to have one for the states. Logically this makes sense. Another option is subaru bringing back a performance hatchback and toyota using that platform to make a FWD sports car, like the Celica. But I think the GR corolla makes the most sense.