I have been around this block before too, and a lot of times a tech company will steadily tell you to pay no attention to the man behind the curtain. However, as long as DNN keeps offering a Community Version comperable to what it always has, I see no problem. The Pro Version should come with support, which would be a great thing in some cases and cause me to use that particular version for larger, mission ciritcal sites.
On the ownside, while you say module development is decentralized, it still depends on developing for the platform. If DNN changes the Pro core to make it different than the Community Version core, then module developers may quit developing for the Community Version.
If they see that there is more profit in developing for the Pro Version, they may simply quit offereing a Community Version module at all and just stick with high-end Pro Version development. I would hate to have to choose the Pro Version because a module I need only has half the features in the Community Version.
Module development has been growing by leaps and bounds for the last 2-3 years and developing Pro Versions or lesser Community Versions may slow that down a bit due to having to charge higher prices for more and better features. Module developers may not see any reason to develop a small but useful module that sells for less than $50 for the Community Version.
Another thing to consider is the competition. DNN has been far superior to many other CMS out there, even expensive ones. This may not remain the case. I have looked at other CMS at times looking for a particular features I couldn't find in the DNN community. Once you have to start paying for a CMS platform, most buyers will shop around before they commit to their purchase and perhaps base that purchase on particular features rather than overall useability.
DNN has been the best bang for the buck, even if I had to buy expensive modules and I could usually talk my client into a happy medium. Having to pay means I won't just settle AND pay for expensive modules. I will start looking at who is offering the features I need. I think a Pro Version may be just the ticket for some applications, I just don't want the module community to start neglecting those who use the Community Version. Or, worse yet, DNN Pro become propreitery module developement does as well.