Depends, this has been a long term issue. People don't save enough, or don't earn enough to save, if a workplace plan isn't an option. People over spend. People get bored.
Heck, at my first job, the gray beards would morbidly joke that within a year or less of retirement, most of the guys die.
But I've known many that retired well, or even early, and still are and are quite happy. Now, some of them have odd jobs, or coach baseball, etc. My mom still works for the church as a sacristan, so it's not a ton of hours, and she'd usually be at church anyway. ha. But, she's retired, otherwise.
We also need to keep in mind, a low number, that doubles, is still a low number, but a massive change in growth (100%!). Also, we will have the most people around the age of 65 than we've ever had. So, again, the Boomers tend to skew statistics.
I think it's something worth watching, but I'm not ready to go doom and gloom on it.