@DrinkUrPotatoes Now technically the admins did change their minds on T4 after about a year of nos. The issue with new cods is the closer you get to the latest cod, the more likely Activision will care enough to send a cease and desist letter. There are always reasons to make a custom client for any cod game but in T7's case most of what a cod client would do is already done. Custom clients exist to provide updates to patch security flaws and exploits, and add new features such as dedicated servers, mod support, and anti-cheat measures. T7 already has mod support and dedicated servers( though not for zombies ), as well as an anti-cheat. While there are probably exploits they aren't as well known and as abused as say IW5 or T6.
Additionally, if Plutonium cannot improve enough beyond what the base game already has going for it, it is unlikely that the client will attract many players other than people who just want the game for free.
The most important thing to note is that custom clients are never intended to just be free versions of the base game. If the admins wanted to they could add steam checks at any time.
Right now Plutonium supports 3 games and any additional games would require more developers to maintain consistent updates. Plutonium is a hobby project, so every developer is working on it in their free time.
Case in point until someone gives a better justification than "i want gaym freeeeeeee" I highly doubt any of the newer cods will be worked on now or in the future.
