I thought about that, then dismissed it after less than a second. They have too much stuff going on the future: the 29th Century, the 31st, the 32nd... I can see them writing off Captain Braxton and Daniels as "Possible Futures" but they promoted the later seasons of DSC as "The Future". And I don't see them calling Disco a "Possible Future" at this stage.
So I took "The Last Generation" to mean "The Previous Generation". Let's be honest: "The Last Generation" sounds a lot better for a title than "The Previous Generation".