In 2022 (or therebouts) a new National Spatial Reference Frame (NSRF) will be released by NGS.  This updated National Spatial Reference System (NSRS) will do away with NAD 83 and NAVD 88 datums and rely on GNSS infrastructure and an updated and time-tracked GEOID model.  Montana State Plane Coordinates will also be affected as NAD 83 is left behind.  Learn more about NGS datum naming conventions HERE.

Currently, this State Plane Coordinate System update is open for comment until August 31, 2018.  READ THE DRAFT POLICY HERE.  Email your State Geodetic Coordinator to submit your comments.  [email protected]

From the NGS website:

Through a concerted outreach effort by NGS, each state will be given the opportunity to update their State Plane Coordinate system, with the roll-out of the four new terrestrial reference frames. Any requested changes to the system must be in accordance with the NGS Policy on Changes to State Plane Coordinate Systems.

Should a state decide not to provide any feedback, NGS will likely define State Plane Coordinates (SPC) for that state through the same projections and zones associated with NAD 83, but with offsets in northings and/or eastings to distinguish these new coordinates from the SPCs of NAD 83 and NAD 27. As SPCs are a user-driven commodity, NGS is not expending any resources at this time investigating the improvement of this system.

Learn more about the replacement of NAD 83 and NAVD 88 on the NGS website.