I too was over there in Stans last year, and spoke to a number of the marketing team, who I might add were quite tight-lipped. However, they told me that it would be a twin jet, with a large cargo door and aimed at a niche market. From that, I guessed that it would likely have some kind of rough field performance and possibly be some kind of enlarged PC-12.
I've since read in the aviation press that Pilatus are looking to develop the Grob SPN design. Who knows what will be the end result. Speculation is a wonderful thing don't you think?
One thing is for certain - Pilatus are a clever company and don't jump into anything lightly. They have a canny ability to provide niche aircraft that work, so I have no doubt they'll manage it again with the '24. Having said that, it would be a brave CEO to authorize a new-design business jet in this economic climate. They'll have to pull out all stops to make it special.
I'm waiting so see it, but won't be surprised if it is delayed a few years...