First the good news. OGC's Architecture Board (OAB) has approved our request to send GeoPackage 1.2 to the Technical Committee (TC) for an electronic adoption vote. This vote will start in a couple of weeks and there is a high likelihood that this version will be fully adopted by OGC by the end of June.
The bad news is that the Elevation Extension has been delayed. The OAB requested that the extension be removed from version 1.2 so that it can be worked on separately. The feeling was that elevation data was too important to be rushed and that more time was needed to align it to other parts of the OGC baseline including things called "Geographic information — Schema for coverage geometry and functions" and "Coverage Implementation Schema".
I know this decision will cause uncertainty in the GeoPackage community. The extension does what it does and there is nothing keeping people from using it as is right now. Your mileage may vary. We should probably give it an alias (something without a gpkg_ prefix) to distinguish it from other adopted extensions. Other than that, we will have to wait for the process to play out. I made sure that someone was committed to carrying the extension to adoption.
 This document is dual published as OGC Abstract Specification Topic 6 (Schema for coverage geometry and functions) and ISO 19123 (Geographic information — Schema for coverage geometry and functions).
 This document used to be called GMLCOV but it was renamed when version 1.0.1 was adopted.