AMD has no budget for replacement cards. There is a reason why they are not doing a full lineup now (it does not make economic sense) and there is a reason why they were still selling pitcarin until recently.
Likely Polaris 10 and 11 will go the same way cape verde and pitcarin went. Roadmaps show no successor in the near future for polaris 10 or 11.
IMO Polaris 10 and 11 will be part of AMDs main lineup for at least 3 years.
I said a second revision of the same GPUs once the GF 14LPP process matures. We are likely to see a second revision as its mentioned in the Rx 400 series naming scheme. I do agree that Polaris 10, 11 and Vega 10, 11 will be around till atleast mid-late 2018 when Navi should replace them.
http://videocardz.com/61721/amd-radeon-rx-400-series-naming-scheme-explained
"AMD confirmed they will be using XX5 revisions, which basically means we might be seeing faster variants released after time, when yields are better, leakage was minimized, or AMD simply decided to release higher-clocked version."