If it sells well, Toyota might produce more powerful variants, although the current numbers seem to be underrated.
The chief engineer or product manager has already stated something to the effect that "this is just the beginning for the Supra" - essentially, that there will be more variants, perhaps more powerful ones. It'd have to be a complete flop for that not to happen I'd think
I share your opinion. I loved the FT-1 concept, but I am disappointed on the final production looks and specs. A few pics of the concept.
The decrease in dimensions also affected it's presence and appeal to older generations. It now looks like a underpowered compact Toyota 2 seater (even though it's a Z4 underneath), instead of what we all wanted, the rebirth of the legendary Supra.

Modded Supra does the 1/4 mi in 10.6 secs. This car has barely been released and the aftermarket has already made this car as fast or faster than the heavily modded MKIVs. I'm impressed!

^Yeah, that's how it should've come from the factory.