I think this is an important topic, and it's worth a debate. On the one hand - yes, majority whites. But is it an evil plot against white people?

How about this hypothesis, as outlined in John Glubb's fate of empires:

Empires tend to start as a single ethnic group. Very oikophilic, and over time, move through phases, ending in an oikophobic state with mass immigration - due to the ethnicity in power becoming lazy and ineffectual due to too much success. This happened to the Roman Empire, Babylonian Empire, Assyrian, etc.

If viewing the Commonwealth as a generally unified ethno-empire, you could say the entire empire is now in the age of decadence. An age at the end of an empire, where the empire indulges in the wealth it has accrued, produces little, and simply pays foreigners and foreign powers to produce everything it uses. This inevitably leads to mass immigration, and a lazy in-group populace. It also leads to far more resourceful and productive foreigners, who are competing for a share of the decaying empire's wealth. Eventually, foreigners accrue enough wealth that, when combined with their learned resourcefulness, means they can now comfortably overthrow the empire's in-group.

Obviously there is a lot more depth to the specifics happening today, but as a broad theme this seems a more likely, and historically consistent, explanation.

If you're wondering how an empire can weather the storm: in a lot of ways it can't, it's inevitable for empires to rise and fall. However, the surviving populace within the empire tends to fall back into smaller community groups centred around survivalism, traditionalism, and religion, insofar as religion supports the moral and societal values that allow for community survival and reproduction. These values are forgotten in the age of decadence, and are part of what allow foreigners to out-compete the empire in-group. Groups within the empire that embrace these values, foreign or not, have a good chance of laying claim to the future.