well,This question is refeering to as,you like the guy the same as a bestfriend or at the same level as your best friend?
well,I think you refeered to as you like the guy as a bestfriend but you also feel the emotions of love towards him.
My advice for you would be to not let him go,
I know feelings might change over time and there is a slight percent that you won't be interested anymore. BUT I think that you should first observe what you really feel for him,and if he possibly likes you too.
If you find this emotions and you feel you float while talking to him,and he can't get that smile out of his face,surely youshouldn't let him go.
Possibly you two might be the perfect match.