Valve is probably ignoring TF2 so that fans switch to deadlock which is tf2-overwatch-dota2 adjacent.
That seems malicious, never attribute to malice what you can attribute to incompetence. Valve’s non-standard employee structure means nobody has to work on TF2. There are a lot of other fun things to work on at Valve, not some decades old game that doesn’t make a ton (relative) of money anymore. This is probably the biggest flaw of Valve.
They don’t really work on things that have already been done, but not the way Apple does it. HF3 will never happen, if it does you bet it won’t be the same medium. (think Alyx)