Don’t be afraid to mix and merge.
So you have a fairly successful series going, but now you’re experiencing writers block. You have fragments of two or three sequels written, but don’t know where to take them. You’ve even considered starting on a third, but haven’t gotten anywhere with it. You really like the first two and would love to continue one of them, but each time you get a line in, you stall and don’t know where to go. You wind up stopping for a week, only to come back and repeat the cycle.
Why not take those fragments, as well as your ideas for a third story and combine them? Take the central themes of one, the characters from another, and the story line from the third idea you have, or any combination as such. It may work, it may not, but I’ve observed it working very well for people many times over.
A good example is my book, Magnifica: Gravestalker. I combined a few sequels to create this story as I had sort of written myself into a corner, and my audience was somewhat… upset… with the ending to Magnifica: Tears of the Fallen.
I knew that I had to do something, but I didn’t know what. Gravestalker was a product of the above formula.