I doubt that the Tholos upgrade kits will be a daily prize. As stated, it wasn't on beta (but that can change). It is also the first event that is forcing people to spend diamonds on acquiring the #10 building upgrade (bought diamonds or saved or WW farm world's, doesn't matter).
I feel like it's Inno testing the waters, so to speak, to try and see if more people will spend money on diamonds for it. It's a powerful building, like the PoH and GB, so it's alluring to spenders. If their data says they make more money overall because people spent not only to get multiple copies of the ToI, but also smaller spenders trying to get the #10 upgrade, than we can expect more events like it, requiring diamond spending. If not, then they will probably go back to the PoH and GB layout, allowing F2P players to get a maxed building and spenders just buying multiples.