New Pentax lenses are rumored to be announced this Friday - most likely full frame lenses for the upcoming DSLR camera and the a 24-70mm f/2.8 is a possibility. This rumor was posted on multiple forums and I am not sure about the reliability of the source.
Update: additional information on the new HD PENTAX-D FA 24-70mm f/2.8ED SDM WR lens and WG-40 camera is available here.
