If I had to bet, I would say that there is very little chance of Sancta attacking us soon. It would be a very aggressive gambit on their part and it could easily lead to their destruction.
Assume that they have an army of 4 coming to us this instant.
It will probably take a number of turns for them to arrive. Thinking from their perspective, this would give us plenty of turns to build a counter army. If they lose this fight, it would be terrible for them.
Also, it would be nearly impossible to hold our cities, given our distance to their capital. Of course, they might keep our holy cities. So assume that they destroy us, except for the two holy cities... It would slow their tech considerably until the cities they capture become profitable, and it would leave their homeland extremely vulnerable. Can they afford this? There are 3 other civs on the map.
Now, they don't know exactly what kind of military we have (do they know we don't have copper or iron?). Their army could be defeated, and they are aware of this possibility.
If this happens they would end up making a semi-permanent enemy, and have an undefended homeland...
The thing we have to worry is if they are already allied with Saturn, and there is a combined army heading toward us. If that's the case, the risk for Sancta is smaller... and we are probably screwed.
Or maybe they are just going to kill us "just cuz".
How many turns until we have iron?