Anything that would make the BitShares login as universal as possible is a high priority. Imagine one-click BitShares login to MoonStone, CCEX, CNX Wallet, BANX-EX, etc. That would be utterly amazing. As it stands I know at least MoonStone and CNX Wallet will allow importing your wallet, so I don't think the practical consequence necessarily is that gateways force users to create a new account. They will want to maintain a good public reputation and they also profit from users in other ways, e.g. the fees associated with the instant exchange, fiat deposits, and integration with other exchanges and other cryptocurrencies, as well as probably other things like website traffic and who knows what in the future.