This comment links to Space News' February 6, 2019 article Iridium ends legacy satellite service, switches all traffic to Next fleet which includes the passage:
(Matt Desch, CEO of Iridium) said Iridium has “deboosted” 52 legacy satellites, a process that involves lowering their orbits to catch the Earth’s atmosphere and burn up. So far, 47 legacy satellites have reentered**, Desch said.
Iridium will deorbit the last 13 legacy satellites over the next few months. Desch said the average time between deboosting and complete deorbiting is 19 days.
To supplement @eerie's answer I'll add Scott Manley's latest video Iridium Flares Are Disappearing From The Skies.
For the last 20 years Iridium Flares have been a regular feature of satellite watching as the iridium network provided a nice predictable set of satellites which just happened to produce satellite flares. However the old network is in the process of being replaced and soon you'll not be able to see this phenomena.
"Hello it’s Scott Manley and I’m here today to warn you that Iridium flares are going extinct!"