Based on monitoring of the Steem network traffic by various people, Steemit is apparently planning a secret hardfork of the Steem network (secret in the sense that the source code is not available for public review and I couldn't find a public announcement on @steemitblog either).
One rumor suggests that this hardfork will be to change the powerdown time for Steem to 30 days (something proposed in the past by Steemit Inc), but if this was the only important change being made, it's difficult to understand why the source code is being kept secret.
In any event, without access to the new source code, BlockTrades will not be able build a wallet, which means we will no longer be able to accept Steem as a payment mechanism. Therefore we will be disabling support for Steem as of May 19th (according to rumors, the hardfork is scheduled for May 20th).