1) But Potentially Some Spinoffs
How To Train Your Dragon is one of the most critically-acclaimed and financially-successful franchises Dreamworks has on its books (certainly after Shrek and Madagascar seem to be over). As such, though there are no plans for Dragon 4, the studio will be looking to milk it for some more related movies. Here’s what DeBlois has said on the matter:
“I think I’ve talked [Jeffrey Katzenberg, Dreamworks CEO] down from [a fourth movie]. There may be spinoffs to come, but my involvement and my dedication to completing a story that has a reason for being and a strong sense of integrity and three chapters I think is in place and intact. Everybody seems to be in agreement that we’re moving in the right direction.”
From this we can gather that, though spinoffs are being discussed, DeBlois would take a back seat with these after he’s completed How To Train Your Dragon 3. That sounds like the best case scenario to us. Keep the core trilogy intact, but also produce some off-shoots for fans of the characters and this world to enjoy.