Since in the devout list, they are kept separate,

unlike the one with the bunny girl secretary and Averon when they're sort of merged at first before acquiring one of them as a devout,

and that you have to acquire only one of them to complete the quest with the result of having one devout acquired and the other is left unavailable,

is there still a chance or way to get both of them as devouts in future updates?

Or will they be merged, like the bunny secretary and Averon where they turn into the one devout that you acquired based on your choices?

Ah, right now they're merged - still deciding if one can be gotten with the other, because some people wanted both and were pretty disappointed at not getting both Merile and Averon, too. So we're keeping this in mind for the future!