This is going off a rumor based on a Q and A list from the after party, and one of the things that came up was how to work the new borderlands map into the rotation.
Depending on how the new map is set up, it could work out two ways:
1) If the new WvW map is a replacement of one of the borderlands (all of them are identical), then to make things fair, all three borderlands would need to be replaced with the new one for a given WvW week.
This can be done for all WvW matches, or only a portion of them. So some matches could have the new map, while others have the old.
2) If the new Borderlands is a replacement of all three current borderlands, with individual base camps for each server, it can still be approached in the same way as above. What it would look like is having Eternal Battlegrounds in the middle, with the new Borderlands map surrounding it. The other option is, if the Borderlands is large enough, it can eliminate the need for EB entirely, and the match will be decided based on which server controls most of the map.
Questions that come up:
The new Borderlands has some interesting mechanics to it. Would any of those be used to upgrade the old borderlands? The visual style of the current map can remain essentially the same, but at the very least, the core mechanics of the map should change to reflect some of the new features being introduced in the new map.