It's hard to say much about the next generation mirrorless medium format cameras at this point—even the rumor mill has been quiet—but if you look at Sony's recently updated sensor roadmap, you can confidently assert one thing: the next-gen Fujifilm GFX and Hasselblad X1D models will contain a 100MP backside illuminated sensor with twice the readout speed of the current models.
This is a BIG deal.
It seems like just yesterday (it wasn't) Sony released the a7R II, the first camera with a full-frame BSI sensor. But they're already planning to scale that tech up to medium format in 2018. In fact, their 2018 sensor lineup includes two new MF sensors: a 100MP BSI 44x33 sensor and a 150MP BSI 55x41mm sensor.
These sensors first appeared on the roadmap back in April, but they only received their official announcement on Sony's Semiconductor website on November 9th. That's when Sony revealed the readout speeds of the new sensors, which is what really caught our eye.
The IMX161 is the chip (with some modifications. . . ) that you find inside the current stock of 44x33mm medium format cameras—the X1D-50c, the GFX 50S, and the Pentax 645Z. That sensor's max readout is 3. 3 fps, and it offers 50MP of resolution. The upcoming IMX461 that you'll very likely find in the next-generation models of these same cameras not only doubles the resolution to 100MP, it also nearly doubles the max readout speed to 6fps at 14-bit.
For the next Pentax model, that might not make a huge difference, since it's a DSLR. But for the next Hasselblad X1D and Fujifilm GFX models, which are mirrorless and require on-sensor AF, that will make a huge difference in performance. Plus, the new sensor can record video at both 4K/30fps and 8K/18fps at 12-bit, which means it should comfortably capture the 8-bit and 10-bit flavors we're more accustomed to seeing.
For fans of 'real' medium format digital (55x41mm sensor), keep an eye out for the IMX411 to show up in a PhaseOne camera of the future. That sensor is also backside illuminated, ups the resolution to 150MP, and can shoot 12-bit 4K/30fps and 8K/16fps.
. dpreview.com2017-11-17 19:37