Initial work has been done to introduce mesh layers supporting display of data on structured or unstructured meshes (grids) in addition to raster and vector layers. This is still a work in progress, expected to be fully ready in QGIS 3.4. The work so far lead to creation of a new library MDAL for handling of different formats of mesh-based data and there are new APIs introduced under the hood, however the user interface is not implemented yet.
For more information see: https://github.com/qgis/QGIS-Enhancement-Proposals/issues/119 and https://github.com/lutraconsulting/MDAL
This feature was developed by Peter Petrik and Martin Dobias (Lutra Consulting)