The power of elites is like entropy. A robust society can keep inherited or socially acquired privilege in check for a season or six, but eventually the elites learn a trick too many. Life is a failing of the wing, said Marcus Aurelius, and that goes for societies too.
Cheering rejoinder: societies have very long life cycles, and democracy is a fountain of youth, or rather of regeneration. When elites kill the golden goose, democracies self-correct -- cf. FDR from the left, and Thatcher from the right.
Question of the extended hour for the U.S.: can a democracy kill its own capacity for self-correction? E.g., by Citizens United, or by acclimating its citizens to torture as an entrenched instrument of "national security", or by a media establishment that debases public discourse, or by some tidal pull we don't yet fully understand toward ever-increasing income inequality? There is a battle brewing between remaining democratic antibodies and the instruments of elite entrenchment that have built up since Reagan was elected.
On a social evolutionary plane, too, the issue seems in doubt. On the one hand, take the evidence that Francis Fukuyama has amassed that elites eventually breach the walls that sovereigns erect to limit their influence -- the biological drive to pass advantages to one's children is relentless. On the other hand, democracy has been a durable antidote: in the U.S., at least two cycles of entrenched privilege have been checked or at least slowed, both under the leadership of Roosevelts. In the longest view, no elite is eternal -- except in dystopian visions in which the powerful buy biological advantages.