Not explicitly. Currently, it's the most widest used language for interacting with the VM, but it's not the end development goal. I don't think the entire thing hinges on Solidity, though it's probably the most immediately accessible language. The hype driving the price up seems a bit premature, though.

There are a couple of other languages in development that might improve the ecosystem:

* Vyper https://github.com/ethereum/vyper

* Serpent https://github.com/ethereum/serpent