Well, I think he didn`t promised too much. Because he said that the multiplayer wouldn`t be in there from the start BEFORE the game was available. It`s not like he just waited for us to discover it. When a game or a software is in developement for the open market (not on customers request) the content constantly changes. And he just shared what he put in or left out. So he didn`t promised, it was there from the very beginning. He said, that it is in developement. And that`s the case. For me is rellevant what`s written in the product description when I buy it. Like the ingredients on food. If it is written there, I expect it to be in there. If not, then not.
Since you asked, a few of the last development blogs prior to game release. While I'm firmly in the, 'CA doesn't owe us anything after all he's done' camp, it does seem that multiplayer was one of the major planned features during development, and I can understand that many have looked forward to it. http://stardewvalley.net/dev-update-30/ http://stardewvalley.net/dev-update-31/ http://stardewvalley.net/dev-update-32/ And going waaaaaay back to the original website at http://stardewvalley.weebly.com/about.html in 2012, Co-op play is mentioned right up in the main game description.
"Optimizing the game for controllers." Now that is good news; as amazing as this game is controller support is subpar...especially noticeable in the fishing minigame as well as precision movement.
Thanks. In retrospect, it was incautious for a one-person development team to do so, but the fact that he hasn't dropped it after all this time, and despite the huge success of his singleplayer game, speaks very well of his willingness to see promises through. After all, the bloody fields of Steam are littered with the corpses of abandoned titles and broken promises. CA's not furnishing another.