Yes bmw and Toyota were said to be collaborating on a project for a fair few years now, I've been following this as they're two of my favourite car brands. I'd imagine the z4 replacement will borrow a lot of the tech on this new supra, expect a petrol electric setup similar to the NSX and dont get your hopes up for a manual gearbox.
Supra details: three engines (EU-only 195hp 20i, 255hp 30i, and 335hp 40i - and this means the 380hp Z4 M40i will be offered only by BMW and only in North America and a few other non-EU markets). Intro later this year, common sense suggests it will be simultaneous with Z4. It will be Toyota in name and body design only - everything inside the car is the same familiar BMW stuff: same options, same colors, same interior materials. Speaking of colors, it feels almost like a throwback to the 00s: Glacier Silver, Atacama Yellow, and Crimson Red are coming back, though there'll also be a new matte gray. For the interior, you'll be able to choose between fabric, alcantara, and leather, and (the gods have heard us!) all of these choices will be available in the U.S. Wheels: 17" standard with 18" and 19" optional on 20i and 30i, 18" standard and 19" optional on 40i. 40i gets standard M sport diff, while on 30i it will be optional in something that BMW would call "ZMP". Market positioning for the car seems to be distinctly lower than BMW, for example, the barebones 30i will have manual seat adjustments and no nav system. And, finally (que the sad trombone): all models are automatic only.
As always, it's on the internet so take it with a pinch of salt. But he'd posted that a good while before the details in Best Car came about and they seem to line up so far.