Yes, we need students/citizens to be able to read and write to be effective in the 21st Century, but I don't think adding the R is helpful. There's already a good deal of emphasis on the need for literacy, and if there was anything to be added, I'd make it an L for that, but then we'd have STEALM or probably METALS.
As it is, what's really happening with STEM is much more SteM. There's little being done with engineering, and technology overall in K-12. Yes, technology is used, but the lack of understanding about technology, the computational thinking is missing. So, first I'd like to see SteM education be closer to STEM education, then TEAMS.