Really depends on whether it had stopped fermenting at the gravity you measured . The lowness of gravity only tells you the "thickness" of the fluid - if its a thick beer and stays at 1020 for days , well , then it has probably fermented all its going to (bar priming and carbonation) and will be ready to move on . Unless a lower FG is expected/required in which case the ferment may be wanted to be restarted but thats another story entirely !
Since you have gone on and primed it then I think you may want it a little warmer for a week or so to start the carbonation , but this is dependent on the yeast and I have no idea what yeasts are used in wheatbeers , so my advice there is a little ,errm ,suspect (?) :wha: