[earlz]

There is a way around it, but it's complicated, expensive (in terms of gas), and thus I have never seen anything similar deployed yet.

Basically, use a proxy contract with some form of governance built in to it. The governance is comprised of all Dapp users/token holders/parties/whatever. Using this system, an upgrade can be proposed. The upgrade is a hash of the new contract's EVM bytecode. Then, there are X days for all parties to vote, until Y% approve it (of course, deny or not getting enough votes means nothing happens). Once approved, someone must deploy the new contract code to the blockchain. After the new contract has an address, the proxy contract gets a "finalization" command with the new address. The proxy contract then reads the bytecode of the new contract, hashes it, and compares the hash to the voted on hash. If it matches, then it points to this new contract. Depending on the details, there might be a migration command sent to the old contract, telling it to send coins, state, etc to the new contract and to self destruct. If there are no coins held by the contract, then the state and old code can remain on the blockchain for people who disagreed... Of course, this is stupidly difficult to fully realize in Solidity, but Ethereum has all the features necessary in the EVM. I personally think the faster we can move away from EVM and Solidity, the better off the smart contract world will be.