In my opinion, the 1999 game should never be made. Obviously, everyone has his own idea how that event turns out... and no one could do justice that.
But more importantly: Remember the first time you played AoS. You´re in the same boat as Soma and have no idea what is going on. "What, we are inside an eclipse? Dracula ultimately died in 1999? What the hell is going on here?".
Plus, there´s this guy named J, who makes hints about his past. So you, as a Fan, get a hunch who he really is. And maybe even Soma himself found this man familiar in some way, but this is only speculation on my part.
And then... the part where Soma realizes who he really is. Bam. That´s a suprise. But only if you didn´t read about it on the internet, that is.
So, my point is, there is this unique feeling about AoS that would be destroyed if they ever made that game. Leave it to your imagination.