It strikes me that PDF support, in conjunction with the recent change to bandwidth-based fees associated with stuff sent to @kindle.com for wireless delivery, is a potential revenue-enhancement mechanism for Amazon: PDFs can be HUGE as they tend to have lots of bitmaps and so on. I'm not one of them, but there will always be people who prefer the convenience of wireless even if it costs them something.
One wonders if that isn't reason enough for them to retrofit PDF support to K2/K1. Yes, the screen is too small, but Sony reader seems to do something useful with the same screen size. I'm sure there will be plenty of reasons to upgrade to K3 without holding off until then, and it would remove a competitive advantage vis a vis other readers in the meantime.
None of this alters the fact that PDF is a lousy ebook format, of course.