What about multiple blockchains? And i dont mean competing blockchains, i mean other bitcoin blockchains that use the same bitcoins we use now. These blockchains wouldn't add any coins to the economy and would work entirely on transaction fees. Coins would be added to these blockchains by sending coins from the original blockchain to an address on the new blockchain and coins could be sent back to the original blockchain at any time.

The reason i suggest this is because eventually if bitcoin became a global phenomena, even while pushing the upper bounds of blocksize that the network could handle it could still be the case that transaction fees could be in the range of hundreds or thousands of dollars to get 1 tx included in a block. I dont really know what the solution to this is and admittedly i am grasping at straws here but who knows maybe you guys can take the idea and run with it.