As long as your wheel is based on the DT240 hub you won't have any problem converting it to 11 speed with a new freehub body and an axle end cap. No re-dishing is needed.
No one knows, maybe not even Shimano. We won’t know until they are released and the details are decided on.
I have to admit that my first guess would have been they will be compatible. One would assume that they would just use the same hub body and stick one more cog on the cassette like Campy. There was the possibility that the cassette would bend toward the spokes or something but there would most likely be room.
But the latest rumors are that they are truly increasing the size of the hub body. It would be a possibility that DT Swiss could come out with a new hub body. If the rumors are true then this would affect every DT Swiss hub out there including the Lightweight wheels, Reynolds that use DT Swiss, Zipp wheels built with DT Swiss. Every wheel built with DT Swiss. If DT Swiss could come up with a new hub body there still might be an issue with some wheels with the spokes hitting the derailleur.
So back to no one knows.
I have the design drawings for the new body and there is a length change. The finalized specs have been in the hands of some hub manufacturers since December and most companies already have their new freehub body designs done. The holdup is that nobody can get 11 speed cassettes to test their prototype bodies so nobody has been quick to put them into production yet. However expect to see that ramp up pretty quickly now.
If the freehub is longer, wouldn't that mean the wheel would need to be re-dished?
Not necessarily. On some hubs you have plenty of space on the end cap. So you make the body longer by 1.85mm and the end cap shorter by 1.85mm. It doesn't change the OLN dimensions or the center between the flanges. Hope I'm not just confusing anyone more with my poor explanations.