Q1. Are all the latest release versions of tidyverse and tidymodels packages already using cpp11?
All tidyverse packages that used Rcpp have been converted except for readxl and lubridate. We plan to finish converting the remainder of the packages in the next 6 months.
Q2. C++20 brings a lot of exciting features to the language, do you plan to also add a {cpp20} package too?
I agree! It is possible, but it would not be for at least 5 to 7 years from now, if ever. Compiler support and availablity often lags the language specifications significantly. However you can definitely use C++20 features with cpp11 in your package today if you like!
Q3. So writable:: is like not using const& in Rcpp?