thats not really what happens tho before disney was the big evil king of intellectual property and they were running around adapting other works their stuff was stand alone despite being based on existing stories or being adaptations of existing stories. When superman became more or less public domain we didnt see this happen despite his popularity people just did their own unique adaptation/retelling of the story rather than a mess of sequels. What i think would actually happen is that people would retell masseeffects story with their own takes on it and make new stories in that universe or with the original characters (tho im sure it would happen idk why they are all so fucking bland).

And even if there were unofficial sequels the original studio can always slap a “from the original creators of” label to theirs so people obsessed with the official telling of fictional stories know what to obsess over.