Here's a graphic showing interchangeable lens camera and fixed lens large sensor camera launches by camera manufacturers between 2011 to 2016 Q1. (Click the graphic to view it larger. You might want to download it to see it better if you're on a small screen since it's a tall graphic):
The reason I made this graphic was because I was feeling that Sony's frequent camera releases felt too fast and because of that, I have problems trusting that my camera won't become obsolete (in other words, 'not new') in a short period of time.
What's clear is that most camera manufacturers release about 3 to 4 cameras per year in these categories. I wanted to compare how much Sony is releasing relative to the industry. Sure enough, they're releasing about 6 to 7 new cameras per year. That's about 50% more than the rest of the industry.
From the looks of it, Sony replaces a about camera every year to a year and a half — not much different to other manufacturers. While semi-pro models are replaced every 2 to 3 years across the industry, Sony has replaced their A7 series cameras in a year and a half — only six months longer than a typical entry-level camera replacement schedule. This is one example of why Sony's camera launch schedule feels relentless. Pro models by Canon and Nikon follow the 4 year Summer Olympics schedule.
My takeaway is this — it feels normal to hear from a camera manufacturer every quarter (3 months) and feels too often if it's less (every other month or less in Sony's case). On the flip side, Canon for example, did only 2 launches in 2014 and one in 2015 (albeit for 4 cameras, of which 2 of them were the 5D variants). That felt too little. So, for all you product managers out there, every 3 months seems like the sweet spot in terms of being visible (keeping the brand fresh in the mind of the consumer) and not making people feel you're leaving them behind.
Every year for entry-level cameras.
Every year to year and a half for low to mid-range cameras.
Every two years for upper mid-range to semi-pro cameras.
Every four years for top-tier cameras.
Making people wait 3 years (I'm looking at you Canon and your 5D series) is not good.
Here's the release cadence (click the graphic to enlarge):
Sony's releases have a faster rhythm and so you hear about them more often. Canon is the most conservative with only 2 to 3 launches in a typical year. Fujifilm is doing thrice a year. Leica is trying to keep up with 2 or 3 launches a year. Nikon is doing an unpredictable tempo with their 3 releases a year. Olympus, you can almost set your watch to. Panasonic is keeping pretty good time. Pentax's line-up is pretty small so 2 or 3 a year.
In the end though, it's the quality, innovation, service and of course, price that matters. We're spoiled for choice actually.
Pro-tip: you can pretty much ascertain when a replacement camera will be released by studying the camera release graphic. Of course, completely new camera releases are unpredictable.