Very likely, developers won't be happy if MS stick to DVD.
MS will get some flak if they don't support BD movies as well, look at how hard they're pushing the 360 as your all in one media stop now.
That might be valid, but one must remember that Windows 8 isn't going to include MPEG-2 or MPEG-4 decoders which apparently cuts $10-$15 off the price of windows. Granted if Xbox Next is going to be an entertainment hub, the decoders are going to be in there and someone's going to have to pay for them. That said even fully featured Blu-ray players are under $100, so maybe that's a factor in the decision?
IMHO if there's an optical drive, it will be both red and blue laser, but probably not have Blu-ray video playback in it. No video played via 1080p streaming isn't going to have the bit rate to compete with 1080p + lossless audio off of Blu-ray, but it is good enough for most rentals (provided you have the bandwidth).
Flash WILL be the future, but prices are still to high for that to be the case today. I wouldn't be surprised to see Xbox Next have a USB 3 and/or an SDXC slot, but for future use.