Apparently, Connie Britton (who plays Rayna) has only signed on for ten new episodes. That may, or may not, be significant, as a further contract may be subject to negotiations as to terms. But it could also imply that her character will be written out half way through the series.
For UK fans, who are well behind in the screening, series 4 will begin its run next Thursday. It is moving channels - its new home being Sky Living. (I've seen no word on whether the 5th, CMT backed, series will make it over here in due course. Viacom have various music channels, but don't air CMT, over here.) However, Sky are probably more likely to see buying the previous series as an ongoing investment - especially as they seem to be advertising the earlier box sets - so I'm hopeful we'll get series 5 too.