I doubt this will be implemented in time to benefit Skyrim, though I certainly hope it would. 15% Extra Storage space can go a long way, since one of the key limiting factors of the Xbox360 games (And thus multiplatform games) is the amount of Data you can cram on that disc.
Skyrim isn't finished yet, so they definitely haven't already started burning it onto disks. They're already starting to roll out the new format for Halo Reach.
However, I don't think this extra space is actually for the game. The main reason why Microsoft is doing this is so they can fit additional anti-piracy tools onto each disk, while giving games the same amount of space they had before.
I'm looking forward to the next Xbox when all of the games can use Blu-ray. That will last a while I'm sure.