So, do you think that Will actually loves Mike? Or do you think it's more along the lines of, "you've been a safe place, I'm comfortable around you, I'm attached"? Which could very well be the case.
I’m probably going to get hate for this, but I think Will isn’t in love with Mike and is just infatuated by him, and if they were to ever get together they wouldn’t work. Let me explain further. There this thing called arrested psychological development when trauma impairs your ability to develop full emotional maturity, and acting emotionally younger than your actual age is known as age regression. We see this with Will actually believing that they’d they’d sit in the basement playing D&D forever, and him not wanting to grow up and get a significant other at the same rate as his friends.
So when it comes to Mike and their relationship, To Will, Mike represents his childhood, & most importantly D&D & the happiness he felt before the reality of the real world hit. For Will growing up means having to deal with his sexuality and accept that he is different. I think Will still has never grown up, & the safest he ever felt was when he was playing games in Mikes basement, away from his home, because Lonnie was a total douche to him. Also the trauma of being taken by the mindflayer has made him attach all feelings of happiness to Mike. Because Mike was the ones who was there to help him when he was in his trance and the person who understood him the most with El disappearing in season 2 and him feeling like he was losing his mind. So no what Will feels for Mike isn’t true love, it’s fantasy. Once all this is over, they won’t have that commonality anymore so they can’t work (other than 2 friends who like D&D, which isn’t enough to build a relationship on. Also, Mike is in love with someone else) 🤷🏻♀️