I'm sure there will be numerous companies making cat-back and axle-back exhausts, and intakes. I'd get these mods. I believe getting 30+ bhp with these two mods would be possible out of this V8, to get 450bhp.
I wouldn't be so optimistic on the intake and exhaust upgrades. The two-stage intake will likely be difficult to improve on, and in super hi-po cars from the factory, the exhausts are usually tuned pretty well and only little gains are left to be had. Through resonance they can cancel out a lot of the sound without a performance loss, so when an aftermarket kit comes out and sounds awesome, you've usually just paid lots of $$$ for a sound increase - which makes you think you are going faster but usually not.
I bet the only significant upgrade for the IS-F in the first year or two will come from some kind of programmer/tuning to unleash the conservative factory tune that Toyota put in there for longevity concerns.