He's on a sabbatical for the whole super rugby season so I think he misses the June test as well.
He is injured at the moment, broken thumb, but too me he was not as good as he was about a 2 years ago. Against chiefs he missed a tackle on Fruean which he would have made a couple years ago and he did the same against the Blues for another try. Cane and Todd are the two main contenders with Ardie Savea also in the mix. I would have Todd personally because Cane is injured at the moment so he can't really put his hand up for a place.
Carter will miss the June Internationals as you say, but he is not quite out for the entire Super Rugby season. He is expected back for the Crusaders in early July, which will hopefully give him a few games of rugby before the Rugby Championship (which starts mid August).
Cane is back from injury now (he started for the Chiefs last week against the Force), and is certainly seen as the next in line for the 7 jersey behind McCaw. The interesting thing about Cane is that he has never really shone that much at Super Rugby level, but has always impressed at test level (despite the fact he is still very young). His style of play just seems to suit test rugby better than Super Rugby. He has many of the same attributes that McCaw has - he is a big physical 7, is a strong ball runner, makes huge numbers of tackles, runs excellent support lines, and never seems to slow down. His ball handling still lets him down at Super Rugby level, and he still needs to improve at the breakdown, but 'pilfering' ability is no longer the main thing the AB's selectors want from their 7.
Matt Todd is next in line after Cane, and I've been impressed with the way his game has evolved over the last couple of years. Originally he was perhaps a bit one dimensional - he was outstanding at the breakdown, but the rest of his game needed work. His breakdown work is perhaps less noticeable these days but his ball running has improved immensely, and he is certainly a more physical player than he has been in the past. Ardie Savea is one for the future and brings a completely different dimension to the 7 jersey with his freakish athleticism, but he still lacks the physicality required at Super Rugby level, let alone test level (though I have no doubt this will come once his body matures). I still believe the best 7 in Super Rugby for the last 3 years has been Luke Braid, but for some reason the AB's selectors don't seem to be a fan on him. He is a deceptively powerful ball runner, offloads as well as any loose-forward, makes plenty of tackles, and is handy at the breakdown. Perhaps the only things that counts against him is that he isn't really a lineout option, but with the likes of Messam, Luatua, and Read this shouldn't be a major issue.
Onto McCaw himself. To be honest I am a bit worried about McCaw. There is no doubt that his age (and the punishment he has taken in 12+ years of professional rugby) is taking its tool. He doesn't have the pace he once had, and because of this he is turning up to breakdowns a fraction of a second latter than previously. This fraction of a second can make all the difference. He is still capable of slowing down opposition ball as well as any in world rugby, however he seldom is able to produce the turnovers that were once his trademark, but he he still gets heavily penalized. These days he is a powerful ball ball runner, he is still a excellent defender (though again perhaps he lack of pace is starting to effect this aspect of his play too), and his leadership and experience in 2nd to none on the international stage. He tends to take some time to build into a season these days so his current thumb injury is a worry. He is still probably our best option at 7 at the current time, but he is certainly nearing the end of his career, and I'm not certain whether his still the best option at 7 in a years time (or even by the end of this year)...
I think with the balance of the 1st choice All Black back row, McCaw now has to do a lot of the tight work, with Messam, as well as his core 7 role. Read is allowed to roam wider and play a looser role. With Luatua at 6, Read takes up Messam's tighter role with McCaw and Luatua plays the looser back row role, who is able to range out wide. McCaw's breakdown work and pushing up in the scrum is still superior to Cane's, not to mention his vast experience and leadership.
Interesting opinion from Andrew Mehrtens on the NZ Stuff website, who thinks McCaw is trying to do too much of everything and not concentrating on his core roles as a 7.
http://www.stuff.co.nz/sport/rugby/all-blacks/9862520/Mehrtens-McCaw-must-do-less-not-more
I think that's a very good summary of what the AB's want from their 7, and is the main reason I don't see Ardie Savea featuring in black anytime soon (as he plays a very different style).
how about James Lowe as a possible Bolter? He looked pretty tasty when I watched the recent Chiefs games.
Lowe has impressed in his brief appearances, but I would say he is very unlikely to feature. He had a breakthrough season with Tasman during the ITM Cup, and has hasn't looked out of place at the Chiefs. He seems to have lost a lot of weight recently, and because of that seems a lot quicker. The challenge for him will be establishing himself in the Chiefs lineup first and foremost, as the Chiefs have an abundance of outside back talent. Unfortunately he is currently injured (out for 6 weeks with a knee injury), so that will make that a lot harder! The AB's have plenty of depth in the outside backs so they aren't really looking for a wing at the moment, but he has certainly made a promising start to his Chiefs career.