A new, heavily improved Noctilux would be possible today - but they need to sell enough of those, they rather improve lenses that are needed for more people (like the 1,4/50 or new R-WA).
Bigger aspherical lenses are cnc-turned (28-90mm, 90AA...) which takes aprox. 8h for one single surface because of the extreme tolerances (<1/1000mm)! I think Leica, Zeiss and Schneider are the only companies today that use this technology in serial production today.
None of the high-speed lenses wished here (2/24, 1,4/28) would sell under 3000€ and they were also very big - we're talking about Leica-quality-standards, lenses that show nearly their full perfomance at open apertures!
The most likely new M-lens would be a 1,4/75AA - it's one of the oldest lenses around and not as exotic as the Noctilux. Maybe they could even use this design to make a predecessor for the R80 (like they did with the 90AA)?
But all lenses are for the full Leica-format, 24mm x 36mm! Leica clearly said that. M8/DMR are just made because of todays technological restrictions - not because Leica wanted them with a crop-factor.