Why do you think so?I kinda feel like it will be happening at some point in the future. How it could look is a whole other topic though I have my ideas I won't get into detail on here.
I can already measure a pretty good guess the overwhelming majority of folks here are disgusted by the idea but I do believe it is both inevitable and to a greater degree necessary to meet varying play styles and preferences.
...Plus, the MMO bubble popped a long time ago. The genre's not as popular as it was in the past plus other factors. This is why I feel NPC party members is inevitable. Time will tell though.