It seems to me that LESS and Sass always had one Achilles heel - debugging. Right clicking on an element that is styled incorrectly and inspecting it is absolutely essential to the process of styling a web page, and without that, these tools had no future. I now believe that this problem is behind us.
As a side-note - there is a bit of a battle between LESS and Sass. I always preferred LESS because it seemed more cross-platform, and closer to actual CSS. However this development seems to suggest that tools are being developed faster for Sass. So it’s now looking to me as though Sass will prevail.