Whether or not that's Jim, I think his segment would have already been filmed because these episodes are pretty involved because of all the research that Ancestry.com does for them. People go overseas, go to different citys to look at old registries, etc.
Production on the 8 episodes began in May, so he might have already filmed his episode, like maybe between the end of BBT and his trip to Paris.
If he hasn't filmed it yet, it seems like it would be a tight squeeze to fit it in before BBT starts in August. He's still filming in NYC and then he has the ZB movie in LA in the next several weeks. Maybe his time on that film won't take long, but it could be unpredictable. I would think that the WDYTYA segment would have to have been done when he had time to go to whatever archives or locations might be involved, since they always like to do that--send the celebrity to their great-grandfather's homeland or whatever.
There are 8 episodes and they don't start airing until July 23rd, which means if he hasn't filmed his segment yet, he'd have to do it really soon and I don't know that he'd have the time.
It seems like I remember reading something some fan or whoever had done and posted online in regard to Jim's family history (or his supposed family history) but I don't remember what it was about.
Do we know anything about stuff like where his parents grew up or if they were always in Texas or whatever?