The following is the trailer for the upcoming Semi-Automatic Classification Plugin v. 3 for QGIS.
Classifications are performed using the spectral signature information. ROIs are used just for the calculation of class spectral signatures. Thus, spectral signatures can be imported from files, and classifications can be performed also without ROI creation.
Classification previews will be performed significantly faster than version 2, depending on the preview size. Also, the plugin interface has been updated with more controls for ROIs and spectral signatures.