Whilst I'm sure there is a vast number of people on this board who are willing to argue at great length why Prior shouldn't be England's first choice keeper for the winter tour of Sri Lanka (and then barring a total dissaster on to New Zealand) like it or lump it he's first choice in Moores's eyes and in the short term that's, however much people may wish it, not going to change. So that just leaves the question of who will act as understudy for him in the test and one day side, which two up and coming keepers get the nod for the A tour and looking lower down the cricketing ladder for the U19's. Given that this has been something of a golden summer for English qualified keepers in terms of performances in the county championship there are a number of pretty useful options of varying domestic and international experience.
The way modern tours are structured means that the reserve wicket keeper has little to no chance of making a worthwhile impression and barring a freak injury will be a glorified drinks carrier for a month which is hardly ideal for an up and coming youngster like Davies, Mustard or Ambrose who would possibly be far better served on an A tour where they'd get some actual game time. For all Read and Foster's international experience picking two proven failures at the highest level (I know I'm being a tad harsh on Foster but he still doesn't impress me as a cricketer) on the back of some pretty unimpressive runs in the second division hardly sends out a great message to the other keepers out there who have worked their backsides off over many seasons for little to no recognition. Players like Jon Batty down at Surrey who is the model proffesional and wouldn't let england down with the gloves or the bat (although it would be mind numbingly dull

) and as Nixon showed at the world cup age really isn't a barrier if the enthusiasm for the game allied to the physical fitness is still there.
Personally I'd still go with Ambrose for both tests and ODI's even though it would almost certainly be a wasted winter for him because I'd still want my best player out there (and one who's argueably good enough to play as a specialist batsmen certainly in ODI's) in case the **** does hit the fan leaving Mustard and Davies battling it out for the A team. In terms of the U19's I don't see any reason to change Dixey and Brown.