NIssan execs had teased a potential Nismo variant of the new Z way back in 2020...I don't think the current reviews are making an impact to the cars timeline.
I think it's a lot easier getting 50HP more HP out of the VR than even getting 10HP out of the VQ. Nissan technically doesn't even need to change a single part on the new Z, literally just new ECU code could do it.
I don't think it's related to this at all. The car was likely planned and in development well before the first reviews came out. This isn't unusually quick for a Nismo model, the 370Z Nismo came out in 2009, the same year the base model came out.
I think we will see it rated at 450HP, a nice even number that is good for marketing, and easily obtainable. Remember, the factory engine can make this with nothing but a ECU retune (especially if you consider it's under rated a bit already)...450HP with a revised intake/exhaust and ECU tune...