The "End of Life" for Joomla 1.5 will be sometime around April 2012.
JUpgrade will migrate Joomla 1.5 to 1.6 and there are plans to support migration from Joomla 1.5 to 1.7 and eventually from 1.5 to 1.8.
1.5 is a long term release which will be supported for around 15 months.
1.6 and 1.7 are short term releases with shorter support periods.
1.8 will be the next long term release (~ 15 months support).
