The S2k is essentially built by hand (aside from like, welding the unibody together) in the same factory as the NSX. It's not a huge profit-maker for Honda so they don't really have much reason to expand the model line.

As far as I know the only changes are the motor, new instrumentation to match the new redline, revised bumpers, different wheels, and the return of the red/black interior treatment instead of the all red option.

With the powerband of the motor as narrow as it is, I think widening it a bit at the sacrifice of 500 rpm at the top end of things will still result in a generally quicker car in most situations. The main problem with the S2k on a track for example, is that it's got the stopping power and handling balance to gain a bunch of ground coming into turns but it's tough to keep the motor in the meat of the powerband for corner exits. If the powerband gets a little fatter than it should be easier to power out of corners and squirt past those heavier cars.