In general it's concerning for any one company to have so much influence in a bunch of different companies in one industry regardless of where they originate.
With Tencent the two main things to be concerned about is China is heavily into censorship so the concern is that might influence the way games are made and developed.
The second is China along with most of the Asian markets are into mobile games and heavy monetization so are we going to see a push towards some of our favorite IPs into mobile games with aggressive monetization?
Remember a game like Diablo Immortal was for the Chinese and Asian markets not the Western markets and while I'm not saying games should only be designed for my tastes and my tastes alone I don't want to see franchises I enjoy be turned into cheap mobile games loaded with micro-transactions either.
Now that's not to say any of that at all will happen and it might be business as usual for Marvelous but it is something to at least keep an eye on.