The current miners are to big and to power hungry. But I think we will see small chips for mobile phones in the next 10 years that can support the network on a basic level. Every hardware POS or wallet needs to be a highly efficient miner. If you have billions of mini-miners then you won't need data centers doing the main part of the work. As long as mining bitcoins is profitable enough we don't need to discuss the next step. We are already on the way to a 1 Watt/THs. Two or four years from now you have chips that can be on every mainboard or as a tiny PC card. The proof of a transaction as difficult as the mining so every device that is somehow connected to the internet can consists this chip and a 2 cent 100gb flash drive for the blockchain (yes future price ). ... and so you have billions of chips supporting the network ^^