I think it's a little premature and negative to go around claiming things like Murray will never win a grand slam. Players with far less fire in their belly and skill have done it in the past, he's only 24 and he shows no signs of giving up his consistent place in the top 4-5 of tennis players at any given moment. He has had to deal with an incredibly british support base who seem to regard every loss in a slam as an unforgivable failure. So he's a little shaky in the first round. So what? Nadal and Federer have shaky early round encounters all the time. Anyone remember nadal's run in with Istomin last year, or Federer with Falla? No-one took that as all that big of a deal back then, and this performance says nothing about Murray.
I believe he'll win slams, he believes he'll win slams and he's fantastic at tennis. It's a matter of time, and maybe we'd all have a bit more fun watching him improve and challenge for slams and we weren't all so damn negative about it.