Okay so with the new card spoiled today (Dragon Egg) my question is whether the "limited" keyword restriction applies to cards being ambushed into play. For example: If I play Dragon Egg on an opponents location could I theoretically ambush 3 Temple of the Graces into play from my hand in one challenges phase?

Correct. "Limited" only places restrictions on how many limited cards you can play in a round. Ambush is a "put into play" effect, so Limited will not apply to it.