I think the chances of having one new episode a week for the foreseeable future are pretty good. Granted, schedules can, and have, changed at the last minute, but I could see them keeping this schedule for awhile. I'm not so sure that they won't air new episodes in the summer. They've done that before with 5D's and since they've already acquired the rest of the series' episodes, I don't really see a reason for them to hold off for a few months, especially if Konami wants them to work on Zexal as soon as possible. As for the ratings issue, 5D's unfortunately hasn't done particularly well in its history on the block, regardless of the time it aired or the seasons, so I don't think that would be a strong enough reason for them to hold off on airing new episodes.
As for the dub staying a season behind, 4Kids actually started airing 5D's only five months after it premiered in Japan. So theoretically, they could still air Zexal sometime in the fall, especially if that second extra ten minutes for the anniversary movie is the sneak peek for Zexal dubbed. It would just depend of if/when they're able to have double premiers for 5D's or if they're able to dub both 5D's and Zexal at the same time. But I wouldn't be too surprised if Zexal would premier next spring either due to their financial status. I think it's a bit too early to tell either way, especially since 4Kids hasn't made any kind of announcement regarding Zexal, although it's practically guaranteed that they're going to license and dub it.
As for the dub staying a season behind, 4Kids actually started airing 5D's only five months after it premiered in Japan. So theoretically, they could still air Zexal sometime in the fall, especially if that second extra ten minutes for the anniversary movie is the sneak peek for Zexal dubbed. It would just depend of if/when they're able to have double premiers for 5D's or if they're able to dub both 5D's and Zexal at the same time. But I wouldn't be too surprised if Zexal would premier next spring either due to their financial status. I think it's a bit too early to tell either way, especially since 4Kids hasn't made any kind of announcement regarding Zexal, although it's practically guaranteed that they're going to license and dub it.