The 1.5 has not been updated at this time and we are still evaluating whether or not to back-port some of the bugs/features from 2.0 to the Joomla 1.5 version. The current 1.5.3 version for Joomla 1.5 is still available to download.
I can understand the disappointment but this is a free product and not part of the club.
It's all about ressources wich are just limited.
That the 1.5 hasn't been updated (this time) does not mean that RT will stop supporting J1.5 templates.
And just to say it ... I stopped using 1.5 already some time ago and won't look back.