From this chapter we can be fairly sure he didn't end up with one of the club members. I would say sensei is a possibility as she is still very tight with his mum and it would be unusual for a teacher to be friends with a pupils mother long after graduating, although not impossible as sensei herself is an unusual teacher, I get the impression any book up would have been above board and after he graduated though. Which leads me to think that maybe he has dated all of them at some point, even if he didn't end up with any of the club members in the end.
He's defiantly not with Ryouko now either because of he was rather than being unemployed he would probably be helping on the farm, even if I'm a temporary basis while he looks for other work. That leaves either the girl from the wrestling club, which didn't feel like Daisuke liked in the way she like-liked him, or Mo-chan.
Reiko has the strongest feelings towards Daisuke of all the ladies in the manga and has been chasing after him since she first appeared and trying to come up with all sorts of schemes (including trying to get over his fear of dogs, just so she can use her cute dog to get closer to him). But I really don't think he even realises Mo-chan feels that way about him. Worth noting that in the character lists in the omakes, Mo-chan is listed first among the non-club members and even before Sensei, so she is obviously quite the big deal in the manga-ka's plans...