Doc Martin Series 7 could be a Rennaisance of sorts for the show.... Doc could finally get more formal counsel in London.....His mother could have an epiphany and really begin to struggle with turning things around for the better.....There could be hilarity in everyone trying in some way to be normal like people in the real world... Then a series 8 could be about many of the core characters settling down alittle but with antics and quirkiness with a sort of been there done that.....followed by a touching and charming series 9 where Doc finally is more of a Doc Sims.....and a mentor.....new life comes in to the village as life goes on.....and tea and sunset moments fall on the charming Portwenn... 
Also, James Henry is growing and he could be around 10 0r older by the end of the series depending on how far they wish to advance the narrative in say 2019. That could be a happy ending of the Doc Martin series and there could be spinoffs or hopes of some sort of brief return series maybe five or ten years later. Then it may have the effects of a tea and coffee...sunsets and old friends type series.