I would think that your target audience for the tutorials is anyone new to VB. However, anyone new to VB will most certainly go the VB.NET route since that is the new technology. Sure, there will be some people that want to use VB6, but that will be a much smaller number.

There will be plenty of people that are happy with VB6, and want to stick with it. But they obviously already know VB6 and would not be in the market for introductory tutorials.