Hornet3d
Wise
I'm pretty sure the answer is yes, Earl. After all, there came a time when users couldn't even open .dsa scene files from DS3 and that didn't slow them down. DAZ has pretty much already done that several times before DS4 and after.
I think that Poser places too much emphasis on backward compatibility, hobbling new features because of it.
I agree, if backwards compatibility restricts new features that also limits potential sales. I think my only concern is if the changes impact an ongoing project. For example, if you are trying to tell a story you want to be consistent throughout so when I switched from V4 to Dawn I had to create a new character and then go back and redo the renders I had done with V4, but at least that was possible, if time consuming. If a new version of Poser converted my old scenes so they could still be used in the latest version that would be fine but if the changes mean I cannot load an old scene I think I would question upgrading.
Poser 11 is a good example, if i was illustrating a book there might be an issue if I suddenly went from Firefly to Superfly but Poser 11 gives me the option to continue with Firefly or update to Superfly and rework old scenes if I wanted to but to do that I must be able to load the old scene which, of course, I can. I am less concerned if, when saved, that scene can only be used in the latest version, such things happen in software all the time.