Strange about myths and legends, they all have some basis in fact.
It is known that Arthur, most likely Artos, was the son of Uther, brother to the war king Ambrosius. The title war king means simply, the guy that leads the all the armies in a time of war.
St. George, aka king George to none Catholics fought and killed something, hence St. George the dragon slayer.
Charlemagne carried the spear of destiny, and one of his lieutenants carried what was clearly a cursed sword, since everyone that owned it died in a most gruesome fashion.
Does this mean that Caliburn or Excalibur does exist? Probably not in the form we are used to seeing in the movies. Artos was pre middle ages, so the sword would be an early longsword based on a roman design.
Plate mail armor wouldn't be around, but a breast plate and shield would be.
Now here be the question of the day, some of the legends hint that should Arthur be needed again, he would return.... Other legends and myths concerning heroes hint at the same thing. So, if they were to return, would that mean the dragons would return as well?
Personally, I could give up all of technology for a world of clean air, dragons, mages etc. The only problem is that dragons are rumored to have very anti social behavior and eating patterns.....