Hi. It would be nice, if the Camera Sony Alpha 7 Mark III could be supported by the open-ended version of Lightroom.
I'm not sure what you mean with 'open-ended version', but if you mean Lightroom 6, then forget it. Sure, that would be nice. It would also be nice if Adobe updated that version with new cameras indefinitely, so your future A7 Mk IV is also supported. But that is obviously not going to happen.
All versions of Lightroom (1.x-6.x, CC2015.x , Classic (7), and Lightroom CC 1.x can use files from any supported camera by leveraging the free Adobe DNG Converter. This tool creates a DNG file form your newer camera's raw file that is completely backwards compatible with any Lightroom version.