I should hope the dev kits have an optical drive.
I got my info from pretty much every gaming website on the internet. It's been a long known rumour that M$ want to ditch the optical drive and go always online. Apparently it's to stop the sales of second hand games like they have done on the PC.
Whether it's true or not? well, they haven't come out and said it isn't.
Either way one thing it most certainly won't have will be a blu ray, given that they would probably rather chop off their own penises than go begging to Sony.
Easiest way to stop the sale of games on the 2nd hand market is to simply use a system like Steam and Origin, where the key is locked to your account.
As for the disc drive issue I think it will have a Blu-Ray since Microsoft will have, no choice but to either license the Blu-Ray or develop there own media that will combat the lack of Blu-Ray.