I got a new rumour - a couple of years from now in an interview GW said that they want to create a edition that would be best and they won't have to rewrite everything in each edition. The reason for that is thay want to go into new directions and explore new places in Warhammer Fantasy. The rumour sais that 8th edition did make that goal and with 9th will see not only The Old World but also Lustria, Naggaroth and mamy more new places.

If that is all true then we can infer a few things:

• As I suspect the geography of the Old World will be substantially altered, probably by the extreme magics thrown around in the End Times, by all sides. Look at the Sundering for ideas on this. My guess is that most of Ulthuan will disappear and the High Elves will have to decamp to their allies in Naggaroth or take over Lustria from the Slann-less lizardmen, for example.
• That the End Times saga will last at least a couple of years. Because of GW's paranoia over its IP, my guess is that FFG will not know how the NEW Old World will look until then. Either that or GW will take the licence back when it runs out in the next couple of years. Either way 4th edition is a long way off.