They don't take local factors into account at all. The local Russian speakers have emigrated at a larger rate than say ethnic Latvians. So, if they just project past trends to the future they are bound to be wrong.

Also, immigration is getting noticeably stronger. And then, the elephant in the room. They don't seem to align these projections with the climate change projections. The Baltics are going to continue to have a hospitable climate with no water availability issues. Unlike most of Southern Europe, and many other places in the world.

So, I'd be willing to put my money against these projections turning out correct.