Dungeons and Dragons, Roleplaying, and my current campaign

I have been running a game of D&D since approximately March/April. I am running it using 1st edition AD&D and the starting scenario used the original Keep on the Borderlands module.

The party has been through a lot, some members have died, others left. They have JUST successfully overthrown an evil cult dedicated to the worship of a dark god who had kidnapped a nobleman's daughter, pretty typical fantasy stuff.

However, we have just come to the end of the content that Keep on the Borderlands provides, and the world has begun to open up (that is, the party is out on their own with no real direction for the first time). I have a few ideas insofar as regions to explore, or dungeon concepts, but I am going to leave it up to them to decide where they will go and when.

The party is averaging a level of 4, and the wilderness is a dangerous place, especially on the borderland. A few of the dungeons I have conceptualized are: The lair of an old black dragon, A massive underground prison built on-top of ancient ruins from a bygone era, and a great well wherein the corpses of the poor were thrown long ago during the time of the imperial rule.

I'm really wondering what the party is going to do, especially given that one of their members has (unbeknownst to the rest of the party) come under the magic influence of some cursed ritual implements that they stole from a dark chapel, and their alignment is slowly ticking over to chaotic.

We'll have to wait and see...