This was a huge rumor in early Feb, originally thought to be starting on Feb 4th. There was a lengthy thread on the rumors page. It was closed a few days later when nothing happened. I spoke to a co-worker whose DW works for one of the Disney focused travel agencies about the rumor this week, and he stated it was happening and Disney had communicated it to her company. He even said they were told it was specifically targeted at leading reservations, not bait and switch cancellations or throw-aways. It was common practice for her agency to get leading reservations for some customers in order to get the "premium FP's". His/her impression was the rule would be FP's made based on timing of the the first part of a split stay would be cancelled if the first part of the stay were cancelled, even if those FP's were during that later part (kept part) of a split stay. Based on that interpretation it is definitely targeted at people doing leading reservations, that they cancel. Since, she just works with cash hotel reservations, she did not know how DVC would be impacted.
I believe that rule of cancelling all FP's if you cancel/shorten a leading reservations would be more difficult to implement from an IT perspective than the one described here, you can only make FP's based on individual reservations, not split stays. Personally, I don't like this method because we do a decent number of split stays and this rule would make me reconsider split stays.
Time will tell......
On a side note, for my May 5-12 reservation I have a split stay (5-10 BCV, 10-12 PVB). When I tried to make my ADR's at 180 days before May 5th, I could only make them for the first stay. MS and the dining reservation cast members "could not do that in the system even for DVC point stays". I had to wait till 180 days in front of the 5/10 to get ADR's for the last 2 days. It may be YMMV on the ADR rule on split stays on DVC points.