Certainly a good question, and tough to answer. It seems to me one of Adobe's recent challenges is innovating on what has become an extremely mature and robust product line. PS is just one piece of that. They may find it difficult to add features to the point of cranking out a new version very 18 months. Also challenging is the entire process of managing versions and the upgrade cycle because so many users are just happy with what they already have. So they have chosen to disrupt the traditional software model they have had in the past (whether good or bad is discussed in plenty of other places) in an attempt to let them perhaps innovate in a different way?
From the things shown here at Photoshop world, it's obvious they are trying hard to innovate in ways to benefit a broad spectrum of their user base (and I don't believe photographers are the majority), and right now they seem to focused on leveraging cloud computing/workflows as well as empowering mobile devices. They demonstrated performing a few operations on an iPhone which the phone itself doesn't have the power to do by using a client server based model. They also demonstrated LR 5's new smart preview technology on an iPad where the entire basic panel was available, and because it's cloud based, those changes were available to the host computer when LR was started and could be applied to the original file.
Not all of the innovation is in areas that benefit most photographers (nothing new there), but certainly some of the ideas will. Only time will tell, but it seems they feel to stay viable and indeed to grow requires a different path. They are aggressively looking for input, and the new model means when they find a cool new little thing, they can just code it and release it. They actually have engineers here doing live coding at the trade show with users ideas ... certainly trying to find out what users want.
For me, 9.95 is a no brainer even if nothing major comes down the line - I'm really happy with what I do and my LR/PS workflow. The fact that I won't have to buy an upgrade just because on OS upgrade killed my program is great, and it's a lot cheaper than upgrading two programs as well as paying for a dropbox account ...
Blizzard has 7 million people paying $15 a month just to play world of warcraft and it's been going for 5 or 6 years now (and they have sold each of those users 4 upgrades at $50-60 each in the process as well). LR/PS for $9.95 or even $19.95 certainly seems a better value than that ...