I have not bought entrenchment but want to. Most of my friends will not be updating. This means what? Will I be able to join their games without a problem or will I not be able to update that system.

Entrenchment is just like a mod, so really

So far, no one from Ironclad has responded, which is kinda sad.    Blair, are you still out there?  Is this sort of an improvement for Entrenchment and the other expansions in the cards and would it be difficult to implement?

I think this issue is worthy of being addressed publicly.  Email is really for technical issues and not feature requests.

The issue is the lobby shows a game available but it is not displayed (as it is a Vanilla game - opposite is true for vanilla people - Ent games are listed as available but not displayed). The only way to see who is in that game and choose if you want to play it is to quit Ent and load vanilla.

When the expansion was coming out, there was a suggestion that the engine would drop back to Vanilla automatically if someone didn't have Sins. This is an important feature was the next 2 expansions can lead to many people having different combinations, not just the 2 options they have now