If the rumoured Sony A7II E-mount camera is real and features 5-axis sensor stabilisation, the below question by Disqus user, iNotFit, is legit:
“So what happens to future FE-mount lenses now—will they be without OIS, hence smaller and cheaper? Or will they STILL need to put OIS on lenses to support the legacy (non-IBIS) NEX’s?”
If 5-axis stabilisation does come to the FE mount, for certain photographers, the A7II could be thought of as a full-frame Olympus OMD. In which case, it behooves Sony to think about possible switchers. With the debut of Loxia and Sony's recent zooms, they have fast to semi-fast glass covered. And at prices that M43 users are accustomed to.
But they don't have slow glass that equates the images output by Olympus's Pro zooms and fast primes: lenses that bring parity between systems would clock in at f/3,5 - f/5,6 on the wide end. If built to enthusiast standards, and with the help of intelligent/informative marketing, they could tip the scales away from the M43 crowd, particularly when comparing noise-equivalent ISOs across platforms.
These lenses must be made with equivalence (explained here, and here) in mind. Or, they should be made with the traditional: providing focal lengths in a number of different speeds. This would tackle the needs of the more-blur-is-better folks as well as the everything-in-focus-all-the-time folks. More importantly, it would establish tiers within the FE mount that explored the freedom enabled by cameras with larger sensors.
The A7 is as small or smaller than most of the enthusiast-level mirrorless competition from any manufacturer; this despite boasting a sensor 2,25x larger than the sensor in the next largest competitor. Informing the customer of how this equates to:
1. better/more options
2. potentially less expensive lenses
3. same or better output quality
4. equivalent sizes
There are a few areas where small sensors, and the attendant wide-angle lens designs drive serious system improvements. But they are few. I'm not a fan of Sony's label-everything design philosophy, nor am I a fan of their build quality. But the full-frame FE mount is exciting. And true or not, the rumoured A7II begs it to be taken much more seriously.