There's a small chance of having a season 4 at all, because Claire Holt is gone, (but might come back) Angus McLaren is gone, permanently, and the only way they could have that working out is if they use my idea of having a whole season to Gracie, Louise and Julia
I could almost garuntee there will be a season 4 mainly due to the way they ended season 3. With the return of Angus (Lewis) they left it wide open for another season. Also why would they stop when the ratings continue to rise and all the actors enjoy it :)
Well I think there will be a season 4 but 5 and 6 no.Season 3 ended like...unfinished.And how I heard in season 4 bella and emma will not be good friends because they think they want to replace each other and at the end they will be best friends.Will and Cleo will be in it too and ash too(emma's boyfriend)but rikky and zane won't be together.I heard that season 4 will be filmed around this year but at the end of 2011 will be launched.I am not 100% sure that's what I heard.
There might be a season 4. It depends on how well season 3 does. If it's popular and they do have another season Emma will probably be back which will make 4 mermaids. Also they'd be out of high school and in college.