We loved the Roku 3's new UI when we reviewed it recently and eagerly anticipated its arrival on "current-gen" hardware this month, but that may not be in the cards. Dave Zatz points out an email sent to Roku developers today that mentions "the new user interface introduced with the Roku 3 will be coming to Roku 2, Roku LT and Roku HD (model 2500) by the end of May." That could add a few extra weeks to the wait for current owners, but there may be a silver lining. The email goes on to mention that it expects channels to run the same, if not better (besides looking better) after the upgrade. We've contacted Roku to find out any more details, we'll update if we hear anything more specific.
Update: Roku has responded, and also mentioned in a post on Facebook that the update will begin rolling out in the first week of May.