I completely agree with the Verilog20 idea. That's the way forward 100%.
Cocotb is awesome in my brief usage so far. The thing that remains to be seen though is performance benchmarking. It would be great to compare the sim runs of two identical tests, one in UVM and one in Cocotb. I highly doubt it could match the performance of a well written UVM test, and this becomes an issue as your SOC gets bigger.