Yes but unbreakable? No-one's unbreakable. To win a Slam he would have to win 7 matches, at least 21 sets. He is going to have to face (short of some bizarre circumstance) at least two of Djokovic, Nadal, Murray and Federer. He may have a killer serve and massive forehand but he's not going to be unbeatable every service game. As proven against Murray this week. Now okay, he did break Murray before-hand and was still able to take the set. But if he can't keep it up over two sets, how's he going to do it over 3-5? Over seven matches?
I can definitely see him winning a Slam one day. But not this year.
As for his record, as amazing as it is, who has he actually beaten? Murray and Tipsarevic are the only names of note that come into my head. He lost to Melzer and Hewitt even. He's done very well but he has only faced any of the top 7 three times (losing in 3 to Federer, in 2 to Ferrer and beating Murray (on his least favourite surface) in 2). I'm not denying that it's a great record so far, but it's to be taken with a pinch of salt.
Good post. There's always this huge hype around Milos as seen last year as well and though some people don't like his style of play including myself, a lot of the people are under the impression as if he's going to take the world by storm and it's mainly because of his big serve. And now that he's gone and beaten Murray, this all confirms to all that when in reality, it's not all it's made out to be and one can definitely look into this post of yours if they want to dig deep. But because Sampras was very successful with his big serve and people somehow see him as the 2nd Sampras (could be most because of Raonic himself as Pete is his idol) coming, those who never liked Sampras are basically freaking out at the “rise” of Raonic. On the other hand, I've noticed that most of the Federer fans are in favour of Milos and that’s mostly because they need someone to stop Nadal and I don't think they feel Nole is enough to stop him and Andy is still looking into things.
But don’t say though that he won’t win a Slam this year. No one saw Sampras winning his first Slam in 1990 when he was still 19 but he did, so anything is possible - though I admit, it will be hard to get by two of the top players, so things will have to fall in his favour. Also, I don’t feel his frame of mind is there yet but I do think he will eventually end up winning a Slam – just how many, I am not sure. It all depends on the circumstances he will have going forward and who will be the players in his time. I’ve noticed he’s quite ambitious, so that ought to take him far especially with the two major weapons he has. Sampras was a mental giant and I am not sure if Raonic is going to be anything like that, though I am sure he wants to be.