While we can speculate...
One thing that will swing me away from the Noctilux for sure is if this lens focuses down to 0.7m... I know there is not much in 300mm, but sometimes you just need to get closer.
Also if Cosina can get their f1.1 to not vignette as severe as the Noctilux, then while you may lose a 1/4 stop in the center, the CV will be effectively as fast overall as the Noct.
Price will come into play to some extent... I hate to hazard a guess where this will land price-wise, but if the Bessa III has taught me anything... then I will plan for the worst case scenario and be pretty pessimistic about the final price.
So taking all the evidence in account, I won't be surprised if this lens pushes over $2000USD, look at the Zeiss 85/2, current price is just short of $3000USD, yes, I know that lens is made in Germany and has the Zeiss label. The Cosina-made Zeiss 50/1.5 is $1000USD. If the price of the CV 50/1.1 comes within $1500USD of the Noctilux, I will still buy the Noct unless the CV lens is an overwhelming winner in close focusing, vignetting and etc.
But I am very, very keen to see this rumoured CV offering... I have no problem with spending less of my hard-earned money for a super-fast 50mm.