I have been experiencing a similar situation, though we were together 2 and a half years, not 10. He was the most amazing BF I have ever had, and our plans for the future were beautiful. Then one day, he started to get grouchy. I thought it was stress. He started ignoring me, spending more time away from home, which was unusual. Then, out of the blue, he just did not come home one night, did not call or text. This man never went ANYWHERE without texting, calling, or emailing me. It has been downhill ever since. The limited number of times I have seen him since, he is a completely different person, very cold and mean to me. I know this is because I was the only thing standing between him and the life he wants to live. He is gone from my life. I am struggling to let go. It has been traumatic for me and I am still in shock, cry every day.
I don't think anyone can tell you whether or not there is hope for a future with your BF. What I can tell you is, this is the fourth time I have been through this, been abandoned by an addict for their DOC, and I have learned that the quicker you let go, the sooner the pain passes. I do know there is hope for YOU, and for YOUR life. There is much in this world to see and do. I have learned that "alone" does not have to mean "lonely."