Your title is misleading to all hell, because you've brought zero new news to light and are basically saying that due to small speculation of one developer and an open ending to an audio drama(made for the sole purpose of making it possible to continue the story) that now there is automatically going to be a X-3 no matter what.
On the other hand, why does this matter if they do make a X-3? Granted, they're milking the universe, nearly to the point where it's almost worse than VII(not just yet, but almost), but if it turns out well, then good. If not, well, then don't buy it. There are still plenty of irons in the fire to wait for, and clearly X-3 isn't even one of them, so if it turns out badly, you lose nothing, but if it's great, you gain a great game.
As for the audio drama bringing back Sin, I'm not going to say whether or not that's good or bad. If they do it properly, maybe it will be alright. As long as they try, it should turn out okay.
On the other hand, why does this matter if they do make a X-3? Granted, they're milking the universe, nearly to the point where it's almost worse than VII(not just yet, but almost), but if it turns out well, then good. If not, well, then don't buy it. There are still plenty of irons in the fire to wait for, and clearly X-3 isn't even one of them, so if it turns out badly, you lose nothing, but if it's great, you gain a great game.
As for the audio drama bringing back Sin, I'm not going to say whether or not that's good or bad. If they do it properly, maybe it will be alright. As long as they try, it should turn out okay.