I'm really not that worried... we're generally not hitting that 2.1 mark anymore, but that doesn't mean white people are going extinct. Rather, we're mixing with others, and so are they.
A big part of it (especially in the US) is our perception of what qualifies as "white". You'll notice that most people of African descent in the US look a good deal paler than their African ancestors, and that's because we've all been intermingling for quite some time now.
The difference is people that are, say, even 3/4 white often wind up listed as whichever minority population they also derive from. Oddly, the census essentially treats "white" or "european descent" almost as a recessive trait, instantly lost the moment it is paired with some other "dominant" minority ancestry. This is, of course, entirely subjective and cultural, but it does further contribute to the sense that white people are disappearing as opposed to just becoming part of the ever-growing "mixed ancestry" group.
There's really little to worry about here. None of this really matters for the most part, and future generations will wonder why any of us even stressed over it in the first place.







