That what I received yesterday from Athom per mail:
“We got a lot of questions about the possibilities to migrate from a normal Homey to a Homey Pro. The short answer to this question is; no, this is not yet possible. However, we are doing our best to release this function in the upcoming two months.
We just wanted to let you know that the options will be available in the near future, so you can decide to wait or to set up your Homey Pro as a new Homey.”