B) 3.5 or Bust! I'm sticking with the man what brought me.
At least for quite a while. We're only three-quarters of the way through 'Shackled City,' right now, and we're going to split my eight players into two groups for 'Age of Worms' and 'Savage Tide' after that. And I've got the Pathfinder books coming my way. I really don't have it in me to pay out - again - for books to do something we already enjoy doing.
Now, don't get me wrong. One of the nice things about managing a bookstore is that I can look at the books - so I'll certainly look at them. But I've got a lot of money and time already tied up into these wonderful Paizo campaigns, and I'm not going to switch to something that would require me to re-work those campaigns that work fine on their own.
So, given that I've nabbed all the Dungeons that had 3.0 or 3.5 adventures in them, and the adventure paths listed above, I have enough to keep playing onward and upward for years.