This picture posted in the dpreview Leica forum seems to be a prototype of a Leica Vario-Elmar-M 28-75mm f/3.4-5.6 ASPH lens. The poster (Dr. Ulrich Rohde) is known to be a tester for Leica equipment. I have no idea if this is an old lens prototype or a new upcoming lens. I asked on social media a week ago and did not get any results.
Update: this is an authentic prototype Leica lens based on the design of the X-Vario zoom. Only 3 lenses were produced (source).
This Leica Vario-Elmar-M 28-75mm f/3.4-5.6 ASPH lens is not to be confused with the already existing WATE (Tri Elmar 16-18-21) and MATE (Tri Elmar 28-35-50) - it is labeled as "Vario" which in Leica's language means a real zoom lens - this is confirmed also in the dpreview comments section:
"This test lens is continuous like a zoom."
"I was asked yesterday to put the M Vario on the SL. This experimental lens behaves like a zoom and I find it extremely well designed."
"First are the 28 mm to 75 mm Leica M Vario, f =4, the M 240 camera does not know the lens.:
Pictured above: Leica TriElmar 28-35-50 f/4 Aspherical (MATE) lens cutout.