We're not saying it's a GS-F, but it's a GS-F.
There isn't much to go on from the teaser Lexus put out ahead of the Detroit Auto Show. The photos shows some sporty-looking components and bodywork, and the press release just says that it will be a performance-oriented F model. That could mean just about anything, but there are some clues which point to it being an F version of the GS. For starters, the RC-F debuted recently, and bringing out something to slot just above that would make sense.
The RC-F also already uses a lot of GS components, so from a technical standpoint it would be an easy transition to make. But probably the most important clue is that spy photographer Brian Williams announced on Twitter in no uncertain terms that the car is definitely a GS-F. He is just one man, and he doesn't say exactly how he knows this, but being that was the most likely possibility for this car to begin with, we're inclined to believe it. But whatever it is, we're certainly curious to see another high performance car, and it doesn't much matter exactly what shape it is.