Will anything extraordinarily bad happen like the game not running and such?
I just thought about it because its 7.81GB of cache files and do I need them or can I delete its contents without resulting in a problem same way as D:\World of Warcraft\Cache?
E.g., if you want to copy your WoW folder to another computer fast, you can skip copying the ~8Gb data/cache folder.
I don't know details of this new caching mechanism, but I can't quite figure out how much performance you can gain if you cache ~8GB worth of data from the ~16GB normal data files.
You can delete this cache, however as explained this may result in longer loading screens as the game needs to rebuilt a local game cache.
This can some some performance issues and crashes however.