I'd hope its flash
A 12x bluray drive will be spining at 10,000rpm which is what a dvd drive will spin at for maximum speed also as past that the disc will shater while spining. So a 12x bluray drive will sound the same as a 24x dvd drive.
For now bdxl is a limit due to the small amount of capacity to make the devices.
however you could just go to flash with 300MB/s and vastly superior random acess to hardrives
If you google around you will find its about 50cents per GB of flash from Intel/Micron press releases
But going to 4 gigs of ram is a 8 times increase in avaliable ram for assets. Going to 8 gigs would be a 16 times increase.
You only need a 8xspeed BR drive to get the same transfer rate as a 24xDVD, unless the Wiki we both are using is wrong. So at any rate the BR drive should be quitter.
And you would need at least a 250GB SSD drive in the future consoles, considering that they will most likely go with 500GB minimum i would be very surprised if they go for SSD considering the price difference.
And of course i prefer flash, if i don´t have to compromise on game content. I hope you are right that the price will be so low that it "wont matter". But i am pretty sure that whatever little cost difference there is at manufacturing it will grow beyond that when we end at retail. If it costs 5 dollars more at manufacturing to create a game that cost is most likely double that when we end at retail. And the 5 dollars is maybe 20 times the cost of a BR disc.
Besides, the idea that the future consoles isn´t able to play Blu-Ray movies seems unlikely to me, except Nintendo that might go back to VHS. I expect MS and Sony to be going out with all guns shooting.