It's just as important to explain what that entails, though. Some stuff that's tied only to this game will stay unfinished, but others will be carried on into the sequel. Just saying "the game is abandoned" paints a completely different picture of the situation than, say, "The developer will be stopping new content in this game to start on a sequel and some content in this one will be left unfinished."
The developer even suggested that they may add some content to this game that transitions into the sequel, implying that they see it as the kind of situation where it makes sense to play Superpowered 1 before Superpowered 2.