According to the NSX-books I have 4-wheel steering was considered in the development of the NSX but not choosen because the engineers felt the extra weight wasn't worth the advantages.
A lot of option were considered in the development of the NSX, like 4-wheel steering and/or 4-wheel drive, electronic dash-instruments etc.
These were all not choosen because the possible advantages were not big enough to make up for the added weight.
If you look now, 13 years later, to the technologies that made it into normal production cars I would say the Honda engineers made the right choices. 4-wheel drive is still not common on normal cars, let-alone sportscars. 4-wheel steering is completely out of the picture. I do not know of any sportscar that has made any impact using 4-wheel steering.