What I'm afraid of most is that dragon encounters will start to inhibit your play experience like the gates did in oblivion. In OB if you wanted to take a break from quests and go exploring, hunting, enjoy the environment, finding ingredients etc you would have to constantly worry about and watch out for the increasing number of gates that were popping up and disrupting your adventures. I know it's been said that some dragons wont attack on sight as soon as you stumble upon them, but I still can't help having doubts...

Dragon encounters need to be fewer in number than gates in oblivion.
They also need to vary drastically in nature, like different locations, dragons bringing the fight to you or attacking cities (i know this is confirmed), awesome dragon AI. Like johnathanwinter said above, having a dragon retreat after it's been injured and forcing you to go hunting after it is an awesome idea.

These two ideas will make the encounters rarer, less repetitive and thus more memorable and epic.

Ah my mistake i misunderstood