I expect we'll see a few dragon fights as part of the main quest, it's pretty much mandatory if you make a game about fighting dragons, but there should be other things involved in the main quest as well, and the majority of dragons are probably not going to be part of the main quest, hence why they can be non-scripted encounters. In this respect, it's pretty much the same as Oblivion, except hopefully dragon fights will succeed at remaining more entertaining than Oblivion gates.
You mean Bethesda is not doing repetitive quests? What about the closing of the Oblivion Gates in TES4?
Only a small amount of the Oblivion gates were actually necessary as part of the main quest, the Aid for Bruma quest also required closing some, but it wasn't essential to complete that quest to advance the main quest, the bulk of the Oblivion gates were entirely unrelated to quests, and you only needed to close most of them if you wanted Sigil Stones. They did get repetitive, yes, but you could complete the main quest while ignoring most of them entirely if you wanted. And you can't call them repetitive quests when there's no quest attached to them, they're just repetitive places to explore.
Better still would be if they've learned a few lessons from Fallout, to the point where you don't actually have to kill ANY of them.
Not going to happen. The point of being a Dragonborn is that you're someone who
kills dragons. Besides, how exactly do you talk you're way out of a fight against a force that is intent on destroying the world?