From what I got, the future should look like :
-You choose the RISC-V design first.
-From that design, you choose the fab that will produce the design. Each fab has its own price and trustfulness.
The 3 big fabs that you'd like to use are fully booked until 2023 or so. So you kind of forgot the "wait 4 years" part.
Maybe, but that would mean building our own hardware. I don't think anyone here would be comfortable with that, we are not big enough for such an endavour to make any sense at all. We'd rather buy off-the-shelf hardware, preferably from a selection of vendors...
Sure, we will fab your design how many units do you need? We can manufacture 2000000 for you. Oh, you don't need that many? Is 250000 low enough?