I just found this wonderful list of all the new pets http://www.petbattles.net/
made by the Godmother over at http://www.alternative-blog.net/
Now after some initial panic and 'how can they do this to us?!' screaming, I calmed down and realized a few things regarding the total number of pets shown, which is 505, and the limit on total pets which is 500.
Firstly, that list is every pet, so it does list some that aren't available on US servers, secondly there's the no longer available ones (although some of them might now BE available due to caging in MOP!) and thirdly, for myself at least, there's the TCG/Store/CE pets which I don't collect.
However assuming they will be releasing more pets in the future, for those who do collect TCG/Store/CE pets and perhaps have or manage to get some of the old no longer available ones, the total we can have seems very tight for collectors.