Did Valve respond to SaveTF2?
A "peaceful protest" to "#SaveTF2" was organised by fans in May to raise awareness of the game's many bugs, its ongoing bot problems, and the general lack of updates by Valve despite TF2's ongoing popularity. In response, Valve said it had heard the game's community.
Team Fortress 2. Good news for Team Fortress 2 fans, especially those participating in the recent #SaveTF2 campaign, a 'peaceful protest' aimed at reminding Valve that their FPS game is still loved and enjoyed by many players in spite of TF2's long standing bot woes.
So, on May 26, the community and many content creators staged a peaceful protest called #SaveTF2. The hashtag trended on Twitter as fans posted comics, jokes, explanations, and memories about the game.
#Savetf2 was a peaceful protest/movement begun in reddit and twitter. It was a push to Valve about the problems plaguing their fifteen year old game, Team Fortress 2.
Last year, Team Fortress 2 hit a new peak all-time player count following the game's summer update, which was supposed to solve some major issues with the game in its current state. Unfortunately, bots still run rampant in online lobbies almost a year later.
The game continues to receive official Valve server support as of January 2023, in addition to new content being released on a seasonal basis in the form of submissions made through the Steam Workshop. In June 2011, the game became free-to-play, supported by microtransactions for in-game cosmetics.
Whether or not a Team Fortress 3 will ever be made is up for debate. Based on what we know so far, we can easily conclude that the game is not in development, and likely won't be for a long time.
TF2 first came out way back in 2007, and is one of the company's most successful and popular games. In recent years it's also had serious problems with bots, which you've probably read about if you've been hangin' around Kotaku.
The game has proved to be popular on Steam, reaching 116.27 thousand peak concurrent players gaming in November 2022.
Dota 2 is a 2013 multiplayer online battle arena (MOBA) video game by Valve.
Why did Valve get sued?
Valve Corp. must face antitrust litigation over claims that “most favored nation” policies for its Steam distribution platform have driven up video game prices across the industry, a federal judge in Seattle ruled.
Neon Prime looks set to be the first Valve release as a game in quite a while. More excitingly, the game also looks like it'll be first Dota release since Underlords. Valve Software is currently in production, and information so far points towards this being a DOTA game!

The question is based on an incorrect premise - That Valve never makes 3 games in a series. That is not true. There are three games in the Counter-Strike series. There are 4 (February 2020), soon to be 5 (March 2020) games in the Half-Life series, and that's only counting games developed directly by Valve.