My DH (MarkRG) and I were on the Member Cruise and everything Andy has told you is correct. The
point chart came out about a month before reservations were taken. The points for our Category 8 were about 6 points higher than if we had booked a 4-day cruise during that same time period.
What made the cruise different (dare I say special because some people were upset with that term)

was that it stopped at
Castaway Cay twice and everyone on board was either a DVC Member or a quest of one. You could pay by either points or cash. There was no exchange fee for this cruise, but if you paid cash it had to be in full on the day of booking. Member Services opened up on a Saturday morning and the cruise was about 90% booked that day, sold out on the following Monday. Additional cabins did open up a little later.
A lot of members on it would like another and yes the 7 day would be a popular choice. I'd say look at the charts for 7 day cruises and that will give you a ballpark.
There has been no definate news that I've heard of regarding another one, but stay tuned!