The original estimate was for April/May. With any complex manufacturing project, things come up that you have no control over. There were setbacks with the analog pads, wifi chips, usb controller, etc. The first big batch of dev boards was destroyed in shipping, and that set all software development back by at least a month.
As things stand now, everybody is hopeful for an Aug. release. It is entirely possible that that will happen, but it is equally possible that some other unforeseeable issue could come up and delay things further. Nobody in a position to know better has ever given a set date for release.
Imagine the grief from this forum if they did announce a set date and something else prevented them from meeting that date. As Gruso says, big companies announce dates when they already have the thing ready. This is not a big company. Pandora devs presumably aren't yet in a position to announce it.