Just the fact that you mustered the courage to speak up in a society where people don't have much to say to strangers is something that probably made a lasting memory on him.
During his next study he'll bring up the issue about the Deity of Christ most definitely, although like you said, it may leave him open to being led through the usual WT reasoning and step by step indoctrination. I guess it's up to him to think about what you shared, and how important his current belief is to him.
Hindsight being 20/20, it may have been easier to share a web address like jwfacts.com in the short time you had to chat, since I'm sure the Witnesses will want him to go to their JW.0rg (and having a place online to contrast the information he gets from the JW's is an excellent resource oppossers to the WT can use easily and effectively : - )