I doubt they would make that many changes at once, although I can see future 360's with a quieter fan. This isnt going to really upset anyone, hell PS2 totally changed their laser, ever tried late games on earliest PS2s? They dont work (The Warriors especially)
I think M$ are quite happy to be considered the 'cheaper' machine, hell its gonna work wonders for the Wii.
As for needing a HD-DVD drive, I dont think anyone minds that much at the moment, and a plug in unit will be enough when there are enough HD-DVDs worth buying.
As for Blu-Ray - LOL! It aint gonna work, its Betamax all over again, harder to say, more expensive to buy, it doesnt matter if it is better, its gonna confuse all the old people out buying presents, hell my grandparents have just learnt how to spell DVD, let alone anything else.
And look at Sony's past history in making new media storage disks, MiniDisc, those rubbish littlel PSP films. Three strikes sony, give up!