What ABT dancer David Hallberg is doing by splitting his time between the American Ballet Theatre and the Bolshoi Ballet is certainly a significant first. The idea of a defection in reverse has some political appeal and working for two companies simultaneously is a huge undertaking.
However, I think he is a little late in claiming that the move represents the globalization of ballet. Major ballet companies have been touring throughout the world for a long time now, certainly through modern times, but I suspect much longer. And it is not just dance companies that get a taste of the global. Individual dancers have spent a lot of effort in their careers moving from one national company to another – either permanently or on some form of exchange such as scholarships. So globalisation of ballet is not really something new. As in most human endeavours, we have lived in a globalised world for a long time. What is different today is that international travel and communications is so much easier, faster and affordable.
I had below a photo of The Australian Ballet touring company picnicking in Odessa Park, USSR, 1988. It was from the National Library of Australia collection but the link now appears broken so I removed it.