I know that dungeons are generally locked to the level you enter them at, but what happens to the outside world and towns when you level up?

If you've found a leveled item somewhere laying out in the world and didn't pick it up, can you come back at a higher level and get a better version of the item or is it locked to the level you found it?

Where do you get the summon dragon priest spell?

Not sure how the overworld leveling system works but items found the overworld items are randomized I think so you'll probably find different items later on.

bump

Chests in the overworld contain loot that definitely scales up with your level. There is one particular chest in a graveyard to the west of Whiterun (headless horseman) that changes its loot depending on when you clear out that graveyard.

I don't know about items that are just lying around outside a container, though. Now that I think of it, I haven't encountered any magical items in the overworld... they've all been normal.

if you let an Item there it will be there untill you take it. I've left a iron enchanted sword in a dungeon and it stills there.

My question about items is more about leveled items then ordinary items, for instance, the chillrend. Could I not pick that up and come back and get a better version or would it be locked to the level I stumbled across it?

and really, what does happen to the people and enemies in the outside world when you level up?

and were do you get the spell to summon dragon priests?