Right, here's my analysis and predictions:
First of all, it's worth having a look at who the All Blacks took on their 2009 end of year tour. Obviously the coaching regime was a bit different, and the squad had three fewer players, but it's ok to use as a comparison at least to some extent. In 2009 the All Blacks took 33 players to Japan and Europe, where they played six matches (Australia, Wales, Italy, England, France, Barbarians). There was an 18 forwards, 15 backs split, and in the squad there were only two open side flankers - McCaw and Tanerau Latimer. This is the first reason why I can't see the All Blacks taking Ardie Savea on tour this year.
With that out of the way, we can have a look at who will definitely be making the squad. It is very likely that almost the whole RC squad will be taken, minus Hore and Conrad Smith. Of the remaining 25 players, Perenara is injured and probably has a 50/50 chance of making the cut. Injuries will likely play a large part in the final make up of the squad, with Todd also definitely out of contention, whilst others such as Romano and Bird are also not guaranteed to be fit.
This leaves us with a core squad of:
Props - Woodcock, Crockett, Franks, Franks, Faumuina
Hookers - Mealamu, Coles
Locks - Retallick, Whitelock
Loose Forwards - Messam, Luatua, McCaw, Cane, Read
Halfbacks - Smith, Kerr-Barlow
First Fives - Carter, Cruden, Barrett
Centres - Nonu, Smith
Outside Backs - Savea, Dagg, Piutau
That's 24 players, leaving us with 12 more spots to fill. If fit, it's likely that the selectors will take both Romano and Bird, and given the length of the tour and the fact that the two are returning from injury we will probably see Thrush remain with the squad in a full time position. There will definitely be at least three hookers on tour, and given his relative experience over the other options, Liam Coltman will certainly fill this spot. Francis Saili will definitely tour, having received his first cap against Argentina. Cory Jane will also probably be reinstated straight onto the right wing, given Ben Smith's move to the centres. With three spots occupied in the midfield, a fourth player will probably be taken, and I think at this point it's a straight shoot out between Taylor and Crotty. Taylor is probably viewed as a better long term option, and certainly offers more utility value, so will likely be selected as the final centre. That leaves us with five more gaps in the roster. A third halfback will be seen as a necessity. If Perenara is fit, he will travel, otherwise Augustine Pulu will probably take his spot. The selectors indicated that Weepu was taken to South African ahead of Pulu due to his experience, but given the weaker tour opposition that won't be a problem now. The final four spots will be divided between outside backs and loose forwards. The players vying for these final spots are Brad Shields, Luke Whitelock, Ardie Savea, Tanerau Latimer, Victor Vito, Johnny McNicholl and Frank Halai. Given the nature of the tour, I think we can rule out the two more experienced, safer options (i.e. Latimer and Vito), this is very much a tour looking towards the future. Halai and Whitelock have both remained part of the training squads for this year (Shields was dropped) so are the probably the first two cabs of the rank. Savea is a prodigious talent, but has yet to prove himself at Super level. I'm more inclined to pick a back straight out of the ITM Cup because the step up is not as extreme. Savea for me needs to tighten up his game, something Shields has shown he is capable of. With only four games on tour, it's unlikely we'll even see Cane start more than one (two at most) matches (consider we're yet to see him start a match where McCaw hasn't been injured), so I can't see a third seed flanker getting any game time. Todd is already in place as a back up for the medium term, should injury strike, and the same goes for Latimer. I think Savea will be an All Black, but I don't think it will be prior to the 2015 World Cup. For that reason, the last two spots will likely go to Shields and McNicholl.
That would leave us with a final squad of:
Props - Woodcock, Crockett, Franks, Franks, Faumuina
Hookers - Mealamu, Coles, Coltman
Locks - Retallick, Whitelock, Romano, Bird, Thrush
Loose Forwards - Messam, Luatua, McCaw, Cane, Read, Whitelock, Shields
Halfbacks - Smith, Kerr-Barlow, Perenara/Pulu
First Fives - Carter, Cruden, Barrett
Centres - Nonu, Smith, Taylor, Saili
Outside Backs - Savea, Dagg, Piutau, Jane, Halai, McNicholl
Possible changes could occur if one of the locks are injured, in which case another prop would likely be added to the squad (Afeaki or Moody). Luatua, Shields and Whitelock can all cover lock quite easily, and there aren't any other locks running around that would really justify selection at the moment. Likewise, McNicholl could also be overlooked in place of the sixth prop.
From this squad, I think a likely lineup to face Japan would be:
1 Crockett
2 Coltman
3 Faumuina
4 Romano
5 Thrush
6 Luatua
7 Cane
8 Whitelock
9 Kerr-Barlow
10 Carter (c)
11 Savea
12 Taylor
13 Saili
14 Jane
15 Piutau
16 Coles
17 Franks
18 Franks
19 Bird
20 Shields
21 Perenara/Pulu
22 Smith
23 McNicholl
Keep in mind this is what I expect the selectors to run with, not necessarily what I want them to do (though McNicholl made me being a bit quick to jump the gun!).