Evolve or Find A Higher IV??

There is baseless speculation that raid bosses will probably rotate soon and Dragonite might become a T4 raid boss. If you don't have an immediate need for evolving, you might wait until the end of Zapdos raids a week and a half from now.

It depends on what level it is. If it is below about L27, I would wait.

What level is your Pokemon and how many candies do you have?

if its 15 att and in the levels greater than 25 i say do it

It all depends on how urgent it is to you to get that dragonite, if you have other attackers, then wait, if you are in need of a good generic attacker, then by all means evolve, more so if he has a 15 attack stat, also if he's below level 20, don't bother, otherwise go for it.