Hi,
Since the development cycle is confidential, it is not known when the TermSet.Export will be implemented.
However, you could submit a feedback at
https://connect.microsoft.com/site428
Connect site is a connection point between you and Microsoft, and ultimately the larger community. Your feedback enables Microsoft to make software and services the best that they can be, and you can learn about and contribute to exciting projects.
Thanks,
Jinchun Chen
Jin Chen - MSFT