Hey Steve, some good questions there and thanks for the interest...
In terms of where to purchase from; You can choose to throw your support either way. Both scenarios benefit us. We are curious about the volume of interest the Pathfinder audience has for this terrain, so a WWG influence isn't necessarily important at the Paizo store. Yes, it does help our pocket book if you purchase at the WWG store but we still pay out a licensing fee to Paizo no matter where the product is sold. We won't have a really clear idea of how popular the terrain is until the associated adventure paths are released and we have a couple months of sales data. The "top download" spot is promising but things are still a bit fuzzy.
Monthly release schedules (you must be psychic!); we've had a lot of back-and-forth discussion with Paizo about this as we've moved through the process. Yes, it is true that the cartography is most often the last thing they get done as a module is completed. And yes it's also true that this leaves us with extremely tight deadlines (or with uncertain delays on the module side). There's also the issue of trying to select locations which work within the scale we need to get things done on time. That's not an easy challenge as not all adventure paths have maps which are suited to this terrain format.
The recent solution we came to was to focus our attention on stand-out locations with greater scope, visual appeal and gaming utility rather than releasing strict monthly terrain just for the sake of doing it. As a consequence, that means we'll be spending more time on big, exciting locations and or jumping around to other adventure paths past, present and future. The "monthly" Pathfinder thing won't be so monthly anymore but this also affords us the chance to keep other non-related WWG projects moving.
Hope that answers your questions
-D