Having a bunch of "free space" that's unused due the cap being too big brings a lot of problems and possible exploits. What centralizes Bitcoin is not being able to run a node in your computer, not the nonsense you are talking about. Bitcoin will never scale to worldwide levels by raising blocksize.
There is no free space. Damnit you guys really have no clue about the blocksize debate and comment on it.
The cap limit is not a default setting.
Blocks wont become 8mb size, and 7.5 mb will become empty.
Blocks will remain the same 0.5mb, but it just lets the maxium reach 8mb if it needs to.
Now i dont think 8mb should be increased immediately, but it should be written into the protocol to increase at some point.
I dont like the command & control aspect of the development. There should not be a need for development anymore. Add a final BIP into it, and then its over.
Developing it further just gives more power to the developers and it creates a centrally planned currency, that is nothing better than fiat.