I think the following, or in combination is more likely:
In trying to make sense out of these recent release developements, going back to E3 when I first began to strongly expect this was going to be the case, many possibilities, pros, cons, considerations, etc. are involved. I have finally concluded what I believe has shaped this scenario.
As we all know, The Holiday season is "the" prime time of the year for game and console sales, particularly in the large markets of the West . That being the case, and GT5 being very likely to be releasable by this years coming season, I believe tremendous pressure was likely brought to bear on Sony from the game publishers, developers, etc. that they did not want to have to compete against one of their heaviest hitters, namely GT5, during that seasonal market. Accordingly, Sony bowed to the pressure counting on the strength of the GT series to overcome and still dominate during the spring season. Hence you have GTPSP currently at the for-front, consuming PD resources and relegating GT5 to March 2010.
This is the only reasonble explanation I can concieve of for this strategy.
Unfortunately, as a result, Kaz as well as the GT5 faithful are put in the unenviable position of having to "take one for the team", as it were.