I doubt that the devs will get permission to put in Unearthed Arcana classes but I would like to see a Theurgist. To me it always made sense that Mystra's clergy would have as many wizards as clerics as devotees and I prefer building caster clerics to martial clerics.
http://dnd5ed.wikidot.com/wizard:theurgy
Arcane domain cleric is probably more likely as its already in the sword coast book
