TimothyM is probably right that Alex will not have much interest in the day to day upbringing of his infant child. However, I also never expected Alex and JJ to be a forever thing so I do expect there will be some falling out eventually and probably because JJ finds someone more interesting who isn't encumbered by being married to Mary Ellen....
Brad has lead a pretty chaotic life so far and I'm beginning to wonder as he is now about forty if he isn't ready to settle down with someone and Marc seems to be a pretty good choice. I never gave Marc much chance when he was first introduced into the story. His insight into the family and their personalities at an artistic level seems almost prescient and if he can use that ability to maintain Brad's interest, it seems like a win-win situation.
My thoughts on Will are still ready for almost anything. While he and Zach are fixated on each other and finishing out highschool together, they are still in highschool and the likelihood that they will maintain a forever relationship as mates is a mountain they still have to climb and conquer.
Wade and Matt are another story. Wade has his definite goals in life and sees Matt besides him. Matt sees himself besides Wade, but what is going to do with his life?
All in all, Arbour has a lot of ways the story can go and I really wonder where it heads after the Streak is finished?