Merlin: McGrath hints at Series 4 Ending 

I wouldn't mind season 10 because I'm not ready to say goodbye yet after 5. There is too much stuff to explore like The Great Purge, Ygraine's death/Arthur birth, Gwen and Elyan's relationship, Gaius's past, Gwaine's past etc. I can't for the finale. Can't believe it's almost over. Time flies