It seems to be Leica’s current strategy to produce a full range of products from basic amateur cameras (the Panasonic re-branded products) to the high-end professional market (the S medium format and now the SL miniature format). The Leica M is as for now the iconic product, but seems to have lost the status as the camera for the professional and is now framed as the camera for the traditionally inclined enthusiast. Below the M the line-up comprised the low end rebranded Panasonic products and the X-series, quickly filled in with the T and Q cameras, both framed as high-grade models. The T offers interchangeable lenses, and an APS-C sized sensor. The Q had a fixed lens with optical zoom function and a miniature sized (24 x 36 mm) sensor. The M offers the classical line of interchangeable lenses and the classical miniature format. Above the M there is the S, framed as the new format for the professional user. If you place the current Leica offerings in a diagram you will see this:
Three formats: 30 x 45; 24 x 36 and APS-C
Three finder systems: SLR, CRF and EVF
Two types: fixed lens and interchangeable lens with AF and MF
The Leica S is 30 x 45, SLR and interchangeable lens, AF
The Leica M is 24 x 36, CRF and interchangeable lens, MF
The Leica T is APS-C, EVF and interchangeable lens, AF
The Leica Q is 24 x 36, EVF and fixed lens, AF
The Leica X is APS-C, EVF and fixed lens, AF
Above the S there is the Sinar range and below the X there are the Panasonic cameras
In this line-up there are obvious holes above the M and below the M. The M itself might be updated to a camera with 24 x 36 mm sensor and AF, but this would require a full new range of lenses. AF lenses are always bulkier than MF lenses and this would jeopardize the M and in addition make the CRF mechanism obsolete. A full range of new AF lenses would certainly require scarce resources and lost of investment money (see the slow expansion of the S lenses and the very meagre range of T and SL lenses). It is an option, but not for the short term. Below the M there is some tiny space between the T and the M, but whatever you position there would challenge the Q and the M itself. The dream candidate for many Leicaphiles would be a kind of Leica CL, but either it is too close to the M or not close enough and will soon lose its market attraction. What about the slot between the M and S? A CRF version with a the large S-sized sensor is unlikely to demand attention (see the Texas Leica made by Fuji). A digital version of the Leica R, but with manual focus and reflex finder would be as unlikely because Leica wants to capture the current digital market, where AF, EVF, and a 24x36 mm sensor are required parts of the Lastenheft, as the success of the Sony Alpha7 proves. The Q has all of these, except interchangeable lenses. The new camera has to be sufficiently different from the M and the T to avoid internal competition and in this perspective the SL makes sense. The SL is a strapping camera, close to the size of the original R8 and the current S. It is also a heavy camera that tips the scale at almost two kilograms with the only lens currently available, the 24-90 mm.
See the listing of dimensions.
Dimensions (HxWxD) and weight in grams
R8: 101 x 158 x 62; 890
R4: 88 x 138.5 x 60; 620
Leicaflex: 97 x 148 x 57; 770
Leica S: 120 x 160 x 80; 1410
Leica SL: 104 x 147 x 39; 847 (with battery)
Leica M/240: 80 x 139 x 42; 680

The Vario-Elmarit-SL 24 -90 mm ASPH has an impressive performance from infinity to the close-focus range and its layout is optimized for fast and precise AF. The MTF graphs promis a performance that lies generally above 60% for the 40 lp/mm and is evidently, but perhaps un-intentionally, extremely close to the S range. The zoom range is almost 1:4, more than the 28-90 range for the R system and the SL lens has a constant 1:2.8 to 1:4. The other side of the picture is a very complex design with 18 elements and four aspherical surfaces. This optical design is un-Leica-like in its complexity, but presumably necessary. The design shows the “Japanizing” of the SL lenses, including the OIS feature (optical image stabilization).

The Leica SL has the potential to be a strong competitor for the Leica S, where its size and weight are not a disadvantage. When compared to the M, it scores high on the criteria of optical performance and versatility. The big Japanese companies follow the strategy for a camera range with clearly segmented areas where one can move upwards in specs and performance. The current Leica strategy is far removed from the clean upward mobility line of Canon, Nikon, Sony and Fuji. Leica is creating a range of cameras and camera systems that overlap each other and that are even in direct competition. Where the Japanese follow a strategy of evolutionary steps, Leica is clearly engaged in a learning process of catching up with the Joneses.