PlayStation 2 still is in the market and uses DVD. DVD technology is already (gasp) 14 years old. By the time the 360 leaves the market (let's say 2014 production stopped?) it'll be 18 years old tech in that console.
Can you imagine a PS2 lasting the (approx. 9 healthy years) it had using CDs (a technology first used for home videogaming in 1991 on the Phillips' CD-i)?
The PS2 generation ended in 2006 (when the Wii entered the market), CD technology was already 15 years old (and like 20 years old for the format) by then and obsolete for home consoles. The question is, will the X360 last a 10-year lifespan using 18+ years old media technology? That's just surprising for a home console. My answer is: no, no, you've got to be kidding me, it won't last 8.