There is no Supra in the works. It is dead and buried right along with the Celica and MR2 The last round of concepts ended up in the form of the IS, and that is as close as you are going to get.
The latest is packing a 5.0L V8.
http://www.lexus.com/isf/
The latest is packing a 5.0L V8.
http://www.lexus.com/isf/