Based on just the television series so far, we don't have much information on what the dragons can do. Certainly more massive damage than direwolves, which means that even without a horde of horsemen, Daenerys is in good shape to retake to her kingdoms and the Iron Throne. And the horsemen will be tempted to rejoin her when they learn of the dragons.
As to the Iron Throne even without Daenerys, it does look, at this point, that Ned is dead - certainly a head that looks like his is on the pole - but it wouldn't shock me if, via some power of the north, he either returns in the future or was not truly killed in the first place. At any rate, in his likely permanent absence, Joffrey continues as the vicious king, with Tyrion to join him as the new Hand.
As I indicated when I reviewed the George R.R. Martin's first novel in the mid-1990s, I'm not delighted with the dragons suddenly reborn at the end of this story. That one development changes the whole story - far more profoundly than even Ned's death - and injects much more fantasy into the narrative, giving it a distant kinship with True Blood, which resumes on HBO next week. But I'll be looking forward to where the dragons lead in Game of Thrones the next season.
See also A Game of Thrones: My 1996 Review of the First Novel ... Game of Thrones Begins Greatly on HBO ... Game of Thrones 1.2: Prince, Wolf, Bastard, Dwarf ... Games of Thrones 1.3: Genuine Demons ... Game of Thrones 1.4: Broken Things ... Game of Thrones 1.5: Ned Under Seige ... Game of Thrones 1.6: Molten Ever After ... Games of Thrones 1.7: Swiveling Pieces ... Game of Thrones 1.8: Star Wars of the Realms ... Game of Thrones 1.9: Is Ned Really Dead?
Special Discount Coupons for Angie's List, Avis, Budget Car, Garden.com, eMusic
The Plot to Save Socrates
"a Da Vinci-esque thriller" - New York Daily News
"Sierra Waters is sexy as hell" - curled up with a good book