I personally don't see where just having DVD will be a serious crutch for the XBox. The levels of problems we're seeing here with disc space filling up are nothing compared to the limitations CD's, not to mention cartridges, were having the previous generation. Most Gamecube games still fit onto one disc, with a handful spilling over into two. From CD's inception with the Sega CD and 3DO, it was not at all uncommon to see games spill over into 3, 4, 5, or even more disks. Cartridges were fundementally limited by not even being able to swing that.
Most games next generation will probably still fit easily on 1 disk, with a good portion of them fitting onto single-sided discs. At worst, you'll probably see a maybe 15 to 20% of games spill over on to two discs, and maybe a handful more make it to three. That's really not an unreasonable amount of swapping. Heck, maybe X-Box will even include a 3 disc rotating carousel to soothe everyone's minds.
Most games next generation will probably still fit easily on 1 disk, with a good portion of them fitting onto single-sided discs. At worst, you'll probably see a maybe 15 to 20% of games spill over on to two discs, and maybe a handful more make it to three. That's really not an unreasonable amount of swapping. Heck, maybe X-Box will even include a 3 disc rotating carousel to soothe everyone's minds.