We started talking about it when we found out that LoT was moving to Tuesdays after The Flash and Arrow was the last DCTV show on the CW. At least, that's what gave me the idea. WA's wedding gets foiled, then the action heats up on LoT, and finally things calm down on Arrow, where Oliver and Felicity decide to seize the day.
That sequence of events makes no sense with moving Arrow after Supergirl and before The Flash. As much as a mini-series feel they might be going for this year, I don't believe they'll have crucial stuff for one show happen on other shows' episodes. Someone mentioned other versions of the characters. That would make sense to me. In general, I think stuff like that, without long reaching consequences, works best for these crossovers, so that the shows are free to pick up their own threads the following week. Which is also why I thought the Flashpoint would have been a great storyline for a crossover. It would have affected other shows, but only for that week. Any permanent consequences could have been contained to The Flash.