I think they'll stick with the incumbents initially - they've been doing the job and deserve the opportunity to continue to do so. However; if Guppy/Brownlie/Henry/Milne can put some red ball performances on the board then things can quickly change. The other factor for the bowlers is who can get the most out of the duke ball... yes, they swing but they can be difficult to control and for some can take some getting used to.
Playing Watling as an opener and bringing in Ronchs is unnecessary imo. BJ is 'keeping well and consistently contributing to a high level with the bat as he is... leave him there - it isn't broke so don't "fix" it.
Milne needs to play some (a lot) of cricket and get some miles on his clock - personally, I'd love to see him play a season (even 2nd XI or league) in England so he gets used to bowling 3/4/5 days a week, rather than be on the periphery of the NZ squad getting a few games/overs here and there. Notwithstanding if he's playing in England we can bring him in at short notice if required (though I'd prefer not to, we have Southee, Boult, Wagner and Braces - not to mention Henry who could benefit from some UK time too).
How good is it that we're talking about who to leave out? We're developing a pool of 15-20 players who have (or could) contribute at test level. Bluddy awesome!