The argument doesn't make a lot of sense, especially as Arch talks about Primaris as the last new faction, disregarding custodes or the multitude of new units being released every few months. GW doesn't have a reason to think their dominance on models is going down, and it's most likely that expanding into animation has caused the company to need yo finally address fan animations as breach of copyright.
About 3d printing, there's not really a lot of reason to do it. If you play WH then it will bar you from stores, meaning you'll need your own private mancave for running games (and if you are competitive you can forget about it). If you paint models then you'd probably want something different if you go that route. And if you collect you'd want it all to be official.