I have just installed AutoCad 2015 to test it out and have come across this problem. I drew a simple box with a hole in it in the WCS. I rotated the UCS along the X axis by 90 degress. Started the line command, snap to the corner of the box (3D snap vertex is running) and the "dynamic line preview" is locked to the WCS until I click an endpoint - then the line is drawing correctly in the UCS, but the "next continuing" line is still locked on the WCS until I click another endpoint. I'm really hoping this is just a simple setting I have missed somewhere, otherwise I will have to uninstall and go back to 2014 as we do all of our drawings in 3D. I have attached a video to show what is happening.
(I had to zip the video to get it to attach)