They are stuck.
Responding to recent rumors neither Christoph Waltz (Blofeld) or Ben Whishaw (Q) would return for Bond 25, director Cary Fukunaga stated the film’s script is still being written.
Who is saying those rumors? We haven’t finished the screenplay, so there is no way that anyone could know that. Those are two extraordinary actors, so if there is space for them in the story, I would absolutely want them there. But I don’t know yet what it’s going to be.