So far I guess I am the only NO vote.
Remember, nature creeps in; faster glass will be bigger. I have 50mm 3.5 and at 2.8 (thanks o Graham!) I rarely use it, except that 3.5 is a bit sharper than the 3.5
In general like a cars red-line, and the reserve on a gas tank-it is there for emergencies, Not normal work. The wider open a lens the less detail, more issue
Laws of physics.
I would rather see better autofocus techniques, maybe a bit better CA control, and yes, a bit chrisper.
There are lots of ways to get light, like, getting more light, ev correction (most backs have at least 14bits, and 8-10 is fine for most work) and the magic ISO (like, bigger, not smaller pixels.
I think we are about at the limit for uncooled sensors (maybe a solid state refrigerator could make a 3 micron pixel work but, if you dont have the photons, you are not going to make an image.
Think ablou it.
regards
Victor