I think that there may be a threesome... but
I believe that Zach is self centered and, although he may love Will in his own way, when push comes to shove, his own interests will win out. Maybe he ends up giving an ultimatum to Will to stay away from Travis but still let Zach have him as a fuck buddy... would Will desert a friend in need,,, I don't think so...
Travis seems to be too paranoid, and rightly so, to be able to be his genuine self and has a long way to go before he can be with Will in an open relationship... this might be a long term development through their college years.
Will is more aware of his strong personality than his father but he will have to watch for any tendency to take over control and fix Travis' problems, only to be hurt and rejected if he steamrolls consent.
I am feeling a huge devastating end game is coming for the three...