i cant say for sure on the RPM limit they can run, i had watched a couple races and could have sworn some of the onboard telemetry was reading in excess of 20k rpm though, but may have been a previous years rerun they were showing.

but high revving motors are just another type of motor you have to build for though. you have to have the right parts in the right combinations. in a piston engine, alot of key factors come into play...when we are talking 10k+ RPM, piston speed becomes a HUGE issue..if they ran a bore/stroke/rod that we do on our cars, they wouldn't last 2 minutes. from what i know they run between a 3:1-4:1, bore:stroke ratio. for example, an 350sbc has a 3.48" stroke, and a 4" bore. they might have a 4" bore and a 1.5" stroke...they still use quite large pistons, but thats because the little stroke they have to run to achieve the rpm they want leaves them no other way to get the most displacement. in terms of piston speed...consider that a 350, at 6000rpm, is making that piston move at 39.5mph...that F1 engine with 1.5" stroke is moving its piston at 39.5mph...but it doesnt do it till ~14k rpm.

that is all the in and outs of knowing what your building a motor for and what you will be doing with it. there is alot more to it because i havent even mentioned the valvetrane or anything...but it does emphasize the point different engines have different purposes and should be built accordingly.

on a side note i dont think they are limiting the revs to make them seek advancements from technology though, i think they are doing it to just plain old slow them the hell down. i mean shit, they are 2.4's, making 750ish..while they dont have a lot of torque, 750hp will still make 200ft/lbs get up and boogity especially in that light chassis.