The Destiny's Child Comeback is Proof: Beyonce is the Invincible Pop Star
This isn't completely or even mostly without precedent, but the rate at which it's happening seems strange; we're generating far more long-term stars, and far fewer future reality show contestants.
One theory: Having become entirely self-sufficient and sustainable (I'm looking forward to The Real Housewives Celebrity Fitness Survival Rehab Challenge, as pitched by the near-sentient supercomputer that randomly generates new Bravo shows), the reality TV industry no longer needs to bid up Vanilla Ice and Flava Flav futures.
Another theory: As so much of pop culture becomes fragmented and niche-y, the space in our pop-star firmament for the world's several-hit-wonder also-rans--the Madonnabe to your Madonna, who rides one style and can't get off before the next one leaves the station--is vanishing. (In publishing a similar phenomenon has been explored as the decline of the "Midlist Author,", who sells well enough to stick at a major house but never becomes a ubiquitous, spinning-airport-rack bestseller.)
So where, 10 years ago, Beyonce might have inspired a raft of pseudo-Beyonces, who released ephemeral pop hits and cheapened the initial impact of a "Single Ladies," now she just inspires us to wait for the next Beyonce song. She's powerful enough, now--so in control of her own image, so permanently fresh, so seemingly insulated from the culture-shifts that used to end careers--that she can use the Super Bowl halftime show to remind us that she's going-on-32 (60 in pop-years), and that she was famous before many of her fans were born.