Well, the people behind the Mill might not being around in 16 years time.
That being said, I would really like to see the Mill make it to Silicon - even if it doesn't work in the end, it's much more interesting to me than RISC-V.
I assume RISC-V appeal is because it's open and thus allows people to explore (proprietary) implementations while maintaining compatibility at the ISA level.
If I understand correctly you cannot do this with Mill either.
Their work looks very interesting, but I'm not drawn in writing an fpga implementation or work on a toolchain for it, since I know any success may be impeded by patents
That being said, I would really like to see the Mill make it to Silicon - even if it doesn't work in the end, it's much more interesting to me than RISC-V.