I think he is a saint. But due to the tempest in the teapot in this country over toll houses, I wouldn't be surprised if he was canonized elsewhere.
I know he's controversial in his own right, but I once read an even-handed assessment of the situation by OCA bishop Tikhon (Fitzgerald), who basically said Fr Seraphim believed in prayer book toll houses, and the argument blew up with the then-Dcn Lev and got out of hand. They were silenced because of the public argument, not because Fr Seraphim was wrong.
Anyway, thats my assessment, but let's not get bogged down in that debate here. I don't think toll houses are a significant problem regardless. Many saints have opinions. Saint means Holy, and that should be our main criterion. I don't think anyone would argue Fr Seraphim is not in heaven, so I fail to see the problem. I hope they uncover his relics someday soon.