Via Twitter – 

We’ve done a lot to improve Direct Messages over the past year and have much more exciting work on the horizon. One change coming in July that we want to make you aware of now (and first!) is the removal of the 140 character limit in Direct Messages. In order to make this change as seamless as possible for you we’ve included some recommendations below to ensure all your applications and services can handle these longer format messages before we flip the switch.

This can only be a positive move by Twitter allowing longer direct messages. 

Source – Twitter