Refferals are slated for Q4 of 2021 later this year
This is detailed in the roadmap which was updated a short while ago here Bitwarden Roadmap
Hope that helps, looking forward to it myself. I personally already highly recommend Bitwarden, as it is a wonderful product I believe in and can happily know friends and family members will be better off with even just the free tier. Should they pay it won’t break the bank either