I truly believe that no dancer nowadays can hold a candle to the original Ashton casts. So much has changed with regards to schooling and technique, and perhaps its simply natural transgression, that the Ashton we see performed now is not as the original was. Even the highly praised, on here, casts I've seen do not have the same effect as the original casts did. I think this also applies to other choreographers, for example Balanchine, although I never saw the original casts for his works. This is, however, not to say that Ashton cannot be performed any more; I just believe it has to be taken into account how much the style has evolved in the last few decades. And that the original cast can never be beaten. Then again, if it was performed much more frequently I might be surprised.
With regards to the thread, I can certainly see many promising ballerinas who will likely make Principal in a few years time. No more names to add to others, although at the moment I see Akane Takada as the most likely to make principal first. However, looking at the male dancers I struggle to see ones who'll make principal very soon. Many of the younger ones, I feel, need a lot more partnering experience and to develop their acting skills. All it will take is a few injuries in the upcoming Mayerling performances and the male principal rank will look very bare.
P.S. I am not a new user, simply someone who hasn't posted for a while and cannot, no matter how hard i wrack my memory, remember my old account details. They were possibly linked to an email account of which the password eludes me.