Hi there, I would like to share our plans on Multi-Vendor development in near future.
1. Mobile application - create you own mobile application for you Multi-Vendor store.
2. PayPal for Marketplace - payment method integration
3. Filter vendor by location and buy product from a certain region (see discussion http://forum.cs-cart.com/topic/51167-)
4. Configurable seller application form - ability to manage fields and look&feel of seller register page
5. Separate checkout for each vendor - ability for vendor receive money directly to his account and use any payments he wish.
6. Admin to Vendor Communication addon
7. Promotions optimization to work fine for vendors
Please let me know is something is not quite clear, and I will provide you with more details.
I can not guarantee that we will implement all of the features, and the more feedback I get from you on required features - the more chances we will implement it.