Having Maggie be Josette makes a great deal of sense, especially considering she "was" Josette for the first two incarnations of the show, and I believe that this is where Depp and Burton will be drawing the most material. It really wasn't until the '91 series when this notion was turned on its head - and while creative at the time, definitely could appear to be "just too easy" for the new version of the show. I mean, most of us have already accepted that this is a given. It might be nice to have it NOT be so.
That being said, as was done with the original show, I think it is entirely possible to have Maggie and Vicki coexist. Maggie, the waitress, is held captive by Barnabas, while snoopy, little governess Victoria gets dangerously close to discovering the secret. However, that would pretty much require two leading ladies, and I don't see the reports leaning in that direction. But, I would definitely like that take on the story.
In regards to Willie, while I was expecting someone closer to Karlen's age (or younger), if they went with a more Renfield-esque character, I can see Haley working just fine.
We just don't know enough at this point. But, I do hope Collinwood maintains a governess, as that really is a key element of Dark Shadows, whether she be Vicki or Maggie, or Josette, it doesn't matter to me, as long as she is included in the story.