According to the Amazon listing for Polish Night Music it's going to be released on March 25th. I've listened to the 30-second clips on iTunes and it sounds beautiful but I'm going to try and wait for a physical release. 

A listing's also appeared on Play.com for a new DVD release of The Straight Story in the UK on May 12th. The Film Four/Cinema Club edition has been out of print for a few years now. Since UK releases are often just ports of French DVDs it's unlikely to include any special features unless a French special edition is imminent.