Murray is defending like 6 or 7 points from now until the the French. He's more likely to become No. 2.
Perhaps so, but it still mostly depends on Nadal's play during the slow hard court and clay season. He has opportunities to pick up points himself where he lost to Djokovic last year. Of the 4, Djokovic has the most to defend, followed by Nadal, then Federer, then Murray.
It should be interesting. I'm curious to see how ready Nadal will be for Indian Wells. I think if he can do as well there as he did last year and not lose points on the hard courts, he'll be fairly happy. And then he should be primed for the clay court season. But if Djokovic and Nadal meet in both of those slow hard court finals, and play like they did in the Australian Open, I think one or both would be lucky to escape without some kind of injury. Hopefully, they'll stay relatively healthy. Mr. Federer is probably hoping to defend whatever points he has up to the grass court season, plus maybe taking a clay tournament like Madrid. But he definitely is preparing himself for the major grass events.