JFBConnect v5.2.1 already supports and describes the new Share button properly. Basically, the "Send" button, which we've supported for a long time, is being replaced by the 'new' Share button. We've updated the text inside the extension already. Now, if you configure the JFBCLike module or the Social features (for automatically adding the social buttons to content), the share button *should* display. The share is being rolled out to users over time, so some users may still see the Send button during the rollout.
I hope that helps explain, but if you have any questions, just let me know!
Thanks,
Alex