Thats valid point. I remember with Audirvana had similar case. I was basically lifetime there by buying license one time and you were sorted. Then all the sudden came new version 2.0 and it went to monthly sub to be able to get new updates. I tried 30 days for free and never used audirvana ever again.
This is possible case IF Roon doesnt promise they will never drop lifetime or with major update version ask all to start paying monthly again.