However, they do not seem to take data over from existing fields. Any plan for this being implemented?
No.
I have about 30 fields that I want to move to 5 different group fields and about 15.000 users. That makes 450.000 fields to update by hand and that is jsut not feasible.
You can try migrating the data using a custom query directly on your database. Data should be JSON stored. Example structure as follows.
[{"cb_text": "Text 1"}, {"cb_text": "Text 2"}]
The above would output 2 rows with the cb_text field in each row being set to the respective values.