I saw that these were done in the past, the last time being March. I think this makes it more fun to have special events on top of the weekly events. I especially liked the double glory when the event card is in your team.
Will this be coming anytime soon? Will it be on a weekly/monthly cycle?
Something different can be double trait stones per battle as well.
Most likely will be. The post I quoted is only 3 days old, and with Sirrian’s post today about their adjustments to the update schedule it’s likely they will probably fit into that some how. (And having to reorganise their stuff to be able to manage that new schedule might be why we haven’t seen any lately)