Preview at WWDC likely in June, followed by September launch.
Apple Extends iTunes Previews to 90 Seconds Internationally
Apple seems to have extended iTunes song previews to 90 seconds internationally. Apple first rolled out 90 second previews in the U.S. back in December, 2010. International song previews had been stuck at 30 seconds.
According to a number of reports, the new preview lengths are available in at least Canada, Australia, New Zealand, UK and parts of Europe. As with the U.S. launch, not all songs will have 90 second previews.
In the U.S., Apple had made the change unilaterally in an email to labels telling them that they would automatically extend previews from 30 seconds to 90 seconds in the iTunes Store in the U.S. It's unclear what was the reason for the delay for international markets.