They may very well be. But a lot of times casting announcements are not made until a movie is just about to go into production or even just starting production. It
could still be months before we hear anything - well, anything that's confirmed. Of course, rumors (similar to the one involving Kirsten Van Wagner as Vicki) may run rampant long before then - and some may even turn out to be true... And for what it's worth, the NYT is certainly sticking to their belief that Helena Bonham Carter will be playing Julia.
And an interesting thing about that is that (unlike the possibility of Van Wagner's casting) no other sites seem to have picked up and run with it. But I suppose the IMDb is more high profile than the NYT's film production area, so who knows how many people other than us are even paying attention to the NYT's listings for DS?