I want a retina display too, but i need a Imac and be bothered to wait until 2015 or even 2016 with a Imac, the reason why i said 2016 is no one knows when a retina display is coming for all we next years imac will more than likely get the thunderbolt 2.0 update but will less than likely get a retina display.
That said have you read todays rumor
https://www.macrumors.com/2013/10/03/new-report-summarizes-display-rumors-for-future-apple-devices/ if not there is no mention of a retina iMac and I believe that you might be gravely dispointed come 2014 and maybe 2015 heres why:
a) Apple is slow at adopting new technology look at the blu ray controversy awhile back you might be waiting until Ultra HD goes mainstream if you can stomach that.
b) The Retina display in Apple's philosophy seems to always fall on higher models, for argument sake lets put it this way:
Phones: Iphone 5s Retina vs Iphone 5c Non Retina.
Tablets: ipad 4 Retina vs Ipad Mini Non Retina.
Laptops Macbook Pro Retina vs Mac Air Non Retina
Desktop Macbook Pro 4K support vs Imac vs Mini Non Retina
c) There is still little software or games that even support retina displays
d) It would sound logical for Apple to double its resolution when it introduces Ultra HD content on its itunes store, or when video cards can handle it.
e) The Imac has just received a huge redesign there might be a possibility that a retina may come in the next redesign.