"IE if you carry the VS pointer another 1/4 inch into the altitude tape window - it is pointing to an actual predicted altitude target ) "
It does sound possible that this could be the case, but you would have to know the time frame. Here's a close-up of the V/S pointer at minus 600 (or thereabouts) fpm.
http://members.ozemail.com.au/~b744er/VSpointer.jpg
It seems to be pointing to an altitude of about -100 feet below the current altitude if you are selecting the right hand side of the altitude tape, or -200' if you are selecting the left hand side of the altitude tape). In this case, the time frame could either be 10 or 20seconds. i.e the aircraft would reach minus 100' in 10 seconds if you chose the right hand side of the altitude tape.
However, would this information be of any use to the pilot? The altitude tape only shows a limited range of altitudes.
Regards.
Q.