Funny thing about Canas - one of the "paok news" instagram accounts had a post a week or two ago where they basically said that he's on his way out, etc etc. Someone responded to the post (tagging Canas) with "oh you were such a great player, I'm sorry you're on your way out" etc etc etc (or something to that effect). And Canas responded to it (via emoticons). So he's basically not denying that he's on his way out.
Long story short, I don't think Canas or Shakhov will be here next summer. IF we get Oliveira, we're looking at a lineup of Mauricio/Wernbloom/Oliveira/Misic, and probably a fifth (Balogiannis? Charisis?). I'd say that's a net improvement, personally.