Will Tumblr and the current DNC get their dream of whitey dying off and a start of a "Progressive POC America"?
Probably not. Whites will exist one way or another. I've known Cantus, Sanchezes, Gonzalezes, Hinojosas, etc. that pass for white, even speak without a Hispanic accent. Demographics are always changing and fluctuating. Hell, if you look at birth rates across the globe, they're actually pretty low in most Western countries. White, brown, black, yellow, it doesn't matter, birth rates are declining for every group. The governments think that importing more immigrants will solve everything, but in truth, that won't help one bit. We're overpopulated, and the last thing we need are more mouths to feed, but no only that, we're in a pretty shitty economic situation. It takes money, and A LOT of money, to properly raise a family. The welfare state can only do so much for the Kebabs. Most of the ones being brought into Europe can't even read, write, or give two shits to learn the language of the country they're in. So when the high paying white collar job or skilled blue collar job comes up, who is going to get it: Heinrich Augsburg, who has a passion and wealth of knowledge for the field he is going into, or Muhammad ibn al-Fickifickin, migrant from Crapistan with a poor command of the German language, IQ of 79, and no skills or desire to learn a trade?
Will /pol/ get it's race war and balkanization?
Generation Z is shaping up to be Generation Zyklon-B. They're much more conservative than Millenials (Praise Kek). How conservative? That remains to be seen. With the possibility of a Califrexit, the future country of The People's Democratic Republic of California might end up being heralded as a beacon of light for a POC ethnostate, with the only caveat for white people being that they have to be gay, trans, or have their girlfriend/wife knocked up by Tyrone to atone for their "white guilt". Of course, this place will most likely devolve into a hellhole, with many trying to escape to the safety of America, or take their chances in Mexico. /pol/ might not get its RaHoWa, but we might see some kind of low intensity race war break out before it gets shut down by the national guard, because really, the government won't let that shit fly.
Am I mistaken on thinking the stats are easy to manipulate for whatever you want to believe and racists are making the dumb mistake of assuming these things are static on top of that?
Demographics, especially those that project shit into the near-future (Like 2050, 2060, etc.) rely on data collected in the present. Everything is constant, and not set in stone. They're called "projections" for a reason. I could project that Europe will be turned into Eurabia by 2030 and made into a progressive Islamic paradise, but out of left field comes a ultranationalist uprising that sees the ethnic cleansing of all Kebabs in Europe, a full-scale invasion of Turkey resulting in the reconquering of Constantinople, and Islam being officially outlawed throughout the West with anyone practicing it being put under surveillance for a short time before being hauled off to a concentration camp, if they're lucky. And I could project that the Democrats will win in 2024 (I'm being realistic here since they don't stand a fucking chance in 2020), but due to California being swallowed up by the Pacific Ocean after the big ass overdue earthquake, the Democratic party loses a staggering majority of its voter base, thus sealing their fate as a failed political party.
TL;DR Shit happens all the time that changes demographics. There's no way to truly tell how things are going to look in the future. People in 1960 thought we would have flying cars in the far off year of 2010. But look at us now.