As of now, they are continuing to move forward with XDC 2017 to still happen as planned at the Googleplex in the United States. At this past X.Org Foundation board meeting, they questioned whether the event should be moved outside of the US given the possibility of travel restrictions by the current US administration. However, due to not having any other organizers ready to go outside of the US and getting short on time, they are planning to proceed with XDC2017 as planned.
Additionally, the travel restrictions for citizens from Iran, Iraq, Libya, Somalia, Sudan, Syria, and Yemen will probably not affect any regular XDC attendees.
The dates for XDC2017 in Mountain View haven't yet been set in stone but should happen in September as usual and the dates should be announced soon. Every year X.Org tends to flip between America and Europe for their XDC event; with last year it was held in Helsinki while XDC2018 should be hosted in Europe for those not wanting to make the trek to the US.
More details via the meeting log and meeting summary.