Hi Brian.
1. Is it possible?
2. If Yes, is it difficult?
If WP E-Commerce is a WP plugin, then you may be able to restrict access to it using s2Member’s URI restriction. [hilite path]Dashboard -› s2Member® -› Restriction Options -› URI Access Restrictions[/hilite]
Or do you mean selling s2Member access through WP E-Commerce? If so, then no, unless you create a customization/hack to achieve it.
3. Is there any way to track purchases and downloads of free materials (i.e., whitepapers, etc) for those who are logged in?
The tracking of what you sell with WP E-Commerce may be a question for them. Or you can try tracking services like Google Analytics or scripts like Prosper202, but this is not something I can help with.
Bonus: I know there’s been chatter about greater integration with ecommerce on the next major upgrade, so when is that expected???
Sometime this Summer is the last estimate Jason gave and that I have. This integration may help in the case of you wanting to sell s2Member access through another system like WP E-Commerce.