From Joomla forum:
According to information at the official site of Joomla and this forum. This provided for the release of Joomla 1.7 in July this year and version 1.8 for January 2012.
Current plan
• Version 1.6.2 on 7 April 2011 (short-cycle version)
• Version 1.7.0 to July 10, 2011 version (short cycle)
• Version 1.8 in January 2012 - (which will release the long-term = 15 months)
I think is better to work on EXPauto for 1.5 version and then 1.8...