From the heavens above website - I believe the deadline of end 2018 was mentioned for the demise of Iridium flares so I guess it's no surprise that numbers are falling.
The end of Iridium flares? Home Several people have reported Iridium Flares not showing up as predicted in the last few weeks. It seems that many of the first generation of satellites are now being de-orbited to make way for the next generation which are becoming operational. We just went through the list of satellites which we have tagged as flare producers and removed over 20 which have already left their operational orbit. The satellites are still there, but because the attitude is presumably no longer being tightly controlled, they may not produce reliable flares. We will endeavour to keep the database up-to-date over the coming weeks using the information on Ron Sladen's status list.
Several of the first generation satellites are presumed to be kept in orbit as spares for the new generation, and it could be that the attitude is not tightly controlled when they are in the spare status, meaning there could be further disappointments with flares predicted for these satellites.
Unfortunately, the new satellites are not expected to produce flares, so it looks like they could soon become a thing of the past.