I don't think Gaynor is leaving. I would like to see a new storyline. They haven't done a romantic story in a while, with all the young single people on PYC they could easily do one.
I think they have to finish storylines though. I mean Gethin in particular, I think its hard to watch, but that situation wouldn't just end and everyone move on. That's what they did with the fire and Macs rape no actual ending.