You’re kind of asking the wrong question. Most of the energy going to that speed goes into aero and road resistance. And time is important – theoretically you could put in a small amount of power and reach that speed – but the limiting factor is how long your legs can manage the power levels involved.
I calculated once that saving a lb off your wheels resulted in an effect equivalent to gaining 0.1W on the climbs (so negligible) but gaining 10W when accelerating your bike in typical singletrack – significant. (Note this was a while ago and I may have forgotten the numbers – it might’ve been 0.5lbs not 1lb)
Aerodynamic and friction considerations won’t change (asuming you’re not getting aero wheels) so you only need to consider the weight. Calculate the energy needed to impart appropriate amounts of angular momentum to the wheels in an appropriate time, and that’s your answer.