I think there will be a Dragonslayer 2. I reckon the plot will be something along the lines of: Grove gets captured by an Ice Dragon. Everyone thinks he's been eaten, but after their experience with Wren and Rose, the group - Leaf, Wren, Sky, Ivy, (maybe Daffodil, Violet,) and Rowan, decide (mainly Rowan) to see if they can find him. 

They look in the Rainforest and are all amazed about all the Rainforest dragons - dragons that can change colour. (Ivy worked out that the purple dragon she and Foxglove saw must have been a Rainforest Dragon.) They also run into Murderbasket again, who explains to them (Wren translates) about the war, and why 'NightWings' and 'RainWings' are living together. (Ivy is shocked that there IS a WHOLE TRIBE of black coloured dragons) Murderbasket also keeps thinking Sky seems familiar, but can't put his talon on it. 

On one rainy night, they see the Ice dragon again, and lo and behold, Grove is being set free from a strange cage that he had been in. Then, a rainforest dragon, night dragon, sand dragon and sea dragon come and join the ice dragon, and Wren and Sky think that the night dragon said something that sounded like a prophecy, but they dismiss that. Dragons probably don't know what prophecies are. 

Grove tells them what happened, and explains the mountain with two fangs, and how the night dragon saved him when he was about to be eaten. He also says he saw a golden dragon there, and Ivy and Leaf are very excited, since they think this is the dragon they are looking for. 

So they follow Wren's map, and it takes a long time, but they finally get there. But when they arrive, there is this massive cloud of battling ice and night dragons, and one ENORMOUS black dragon. Eventually, all the dragons suddenly VANISH. A few things happen, but eventually they get to the top of the mountain and meet 'Sunny', who loves the idea of 'scavengers' who can speak Dragon. Sunny also remembered 'Fluffy' and 'Holler' as she called them, and Leaf sees the brown dragon who helped him up the cliff. 

As they are leaving, Sky sees a dragon. A dragon with smoking orange scales the same colour as his, but so much more vibrant. A dragon with bright blue eyes. And it's like; "Wren. I think.... I think that's my sister." But she flys off before they can meet her, and that's where the book ends.

UPDATED WITH BOOK 14 KNOWLEDGE:

Well I guess this sort of happens but sort of doesn't, as in Pumpkin. Although who knows? Grove could still be Bandit!