Paul, on Pentax lenses:
It is correct to point out that most (14) of Pentax's lens line up is old, i.e. screw drive autofocus, not weather sealed, and designed for their film MF cameras. Not all, but some (e.g. 35mm, 120mm & 150mm) of these are still excellent quality. In relative terms these are not expensive, the price probably being pegged down by the used lens market. The 25mm is indeed new, and so is the 55mm and the 90mm macro. I think these are all weather sealed, and at least one has SDM autofocus. They are expensive, but it would be possible to buy these three and the body plus quite a few FA lenses for less than a P1 back.
Pentax have published a 645 lens roadmap which indicates three new zoom lenses including one wide angle zoom, which will probably be released this year.....but I shouldn't count my chickens!
I don't see many Hassy or P1 owners or organisations wanting to switch systems for many of the reasons you state, it would be too much of a wrench. On the other hand, professional photographers considering moving into MF may well be tempted, especially if there are limited funds to invest. Amateurs like myself who are interested in landscape and architecture, however, are beginning to think that maybe the Pentax 645Z will just be affordable, especially coming from a Pentax 645N system with a fair crop of FA lenses. I suspect there are quite a few in a similar position to myself and this is most likely to comprise much of the 645Z market - i.e. photographers new to MF. The poor development of fast synch flash speeds, use of flu card instead of tethering, fixed integrated backs, etc., will not appeal to the high end professional market who require a tech solution.
In the UK we are fortunate to have a good dealer network of Pentax Pro dealers, (n.b. they have continued to sell the full range of 645 lenses). Is it not likely that if the 645Z takes off, then surely a Pro dealer network and service centre would follow? But yes, it should be the other way round.
Looking forward to reviews of the Z,
Ronnie.