Weibo is on our to-do list of social networks to add later this year. However, it will not be in our upcoming 6.3 release, due out in the next few weeks. For this release, the only new network we're adding is Yahoo. There will also be a ton of other highly requested features.
I hope that helps answer your question, even if I can't give a more firm timeline on when it would actually be available.
Thanks,
Alex