They haven't picked the same element twice in a row since Tyr/Thor, so it's unlikely for the next one to be light again. I'll be going with water/Shiva this time.

Also, more details on Michael's awakening are in. The +double atk buff added to Holy Ascension is +20% (it mutually overwrites with Hercules' buff). The burst performance increase added to San Michel is apparently a 100% +burst buff (like any other) and a +30% to the soft cap buff?