If you want to own a "popular brand" then Olympus just isn't a good choice.
Buy a Canon or Nikon, if brand popularity is important to you. Olympus hasn't been a market leader for quite some time now. And even back then, it was only one of the top five brands (along with Canon, Nikon, Minolta, Pentax), and even then was probably fourth of those five.
There will always be a lot of interest in a new and revolutionary camera like the EM5. It was the first M4/3 camera with the much better 16MP Sony sensor. It was the first Olympus M4/3 camera with a built in EVF. It was among the first "retro styled" camera that started the whole trend. The EM5 spent two full years on DPR's "most popular camera" list due to all the clicks it got.
It really is hard to followup a camera like the EM5 with something even more "amazing." The EM1 was better in almost every way, but it just wasn't a breakthrough camera in the way the EM5 was.
The EM5 might have been the pivotal moment for Olympus and M4/3. After that camera, everything else was evolutionary, and not revolutionary.
While it is very hard to know precise market share, the odds are Olympus has around a 4% or 5% market share today. And remember, the pie is shrinking.
At their peak, market share was around 7% in the digital age, and around 10% in the film camera age.
People buy Olympus cameras because they are different. They tend to offer innovative features (things like IBIS, pixel mapping, and lenses designed expressly for digital), and not because they are a popular brand. They also tend to offer pretty good value, and are pretty well known for their outstanding jpeg engines.
No one else offers as many outstanding lenses that were designed for digital from the ground up. Not Canon, not Nikon, not anyone.
Olympus will probably never be the most popular brand.
The only reason the brand still exists is because their medical device division is so obscenely profitable. If it weren't for that division, Olympus cameras would now reside with Chinon, Contax, Toshiba, Agfa, Konica, Minolta, Topcon, and Praktica as a historical footnote. A fact that makes me grateful for endoscopes.
It also seems that the medical device division saved Olympus from gross fiscal mismanagement a few years ago. In business, there really is no substitute for making profits. As long as you are profitable, you can get away with almost anything.
It might be nice if Olympus was a more popular brand. At least then we could find their cameras at more retail outlets. And we wouldn't have to worry about whether their imaging division will someday be shut down, or sold off.
But in the meantime, many of us are very happy with their cameras and lenses. And all those outstanding Panasonic cameras and lenses are just icing on the cake, giving us more, and sometimes even better options.