I really hope Larian stands by their promise to implement all the player handbook's subclasses.
Wild Mage is my all time fav DnD subclass. I also don't think it would that hard to implement. The game would role every time you cast a spell of at least 1st level (cantrips cannot surge), so you have 5% chance to trigger a wild surge every time you cast spells.
Also, the 5e wild magic chart is not that outrageous to interpret into a pc game, with some modest altering.