I’m not yet convinced that the opportunity of staking in Casper will outweigh the risk of having your ETH controlled by a hot wallet. With storage, your ETH can be secured by a cold wallet, thus is significantly lower risk.
As a user, I’ll need pretty solid returns from staking to convince me to bring my ETH out of cold storage. However, having my ETH locked up in a contract that is recoverable by my cold wallet is not really a different risk profile from storing in my cold wallet directly.