I think that Pentax doesn't need to release a new camera every 18 months or so, how it did with K20 to K7 to K5.
Because the cameras pentax has release cameras at that rate.
Look at Canon 5D series life line. The original 5D was released in 2005. 3 years later, in 2008, the Canon 5D Mark 2 is released. 3 years later, 5DMk2 is still a stellar camera. It speaks for itself.
It does so because, so far, it didn't have competition with full-frame, high pixel count cameras releasing more frequently.
Pentax needs to put together a great, complete DSLR, (FF or APS-C) that will have a long life line, and NOT compete with the 18 month life cycle DSLRs. They should release something with great AF tracking, FPS, and image quality that will stand the test of a 3 year life life, the way Canon 5D series does. From 2008 to 2010, Pentax put work into 3 successive camera bodies. In 2008, Canon just kept releasing firmware for 5DMk2 and it's still selling.
So there are a couple points here. First you talk about "great AF tracking". Clearly that problem is much easier said than done. If it were easy, Oly and Pentax would have done it already. They haven't. And, all you need to do is look at Canon's issues with focus in their 1dIII ad 1dIV to see that it's VERY complicated at the high end to "get it right". Of course it's even more complicated by the notion of these large file sizes and the processing power necessary to do the complicated focus tracking and metering and file movement. That's huge. And, unlike sensors, you can't rely on another company to do it for you.
As to the 5dII - the focus system is decent, but certainly not great. The focus system is NOT what sells the 5dII. It's not. The 7d has a better focus system, as does the D700 in nikon. The focus system of the 5d is probably it's weak point.
And that brings us to the next point - Pentax uses Sony sensors. So do Sony and Nikon. You're not going to have much of a competitive advantage using the same sensor as the competition. There are some minor advantages - mostly over sony right now because of how they implement. But no real advantage over Nikon in a segment where Nikon is releasing cameras every 18 months or so. So, to accomplish what you want, Pentax needs to use a sensor the competition is NOT using in their 18 month life cycle cameras.
Why must Pentax release their main DSLR every 18 months? It like quicksand.
Because they don't have a class leading camera concept. The k-5 competes with the D7000 / d300s and 60d/7d cameras. Without very significant strides in focus system performance, Pentax can't be class-leading at the d300s/7d level for sports/wildlifel. Just can't. When you're talking about other types of photography, then you're talking d7000/60d - so now sensor performance is paramount. Now we're back to Pentax having a sensor no one else has that will last for 3 years with no one else leap frogging.
The alternative is to try and compete with the full frame guys - like it or not full frame will always beat aps-c for IQ and noise when you're talking same vintage. So, the next full-frame sensor will again push ahead of the sony 24mp aps-c. So, to accomplish what you want, pentax would have to go that route. And, there are plenty of posts here about why pentax won't go full frame.
It's a catch-22. They're not up to snuff with the 7d/d300s. And they don't have the long lenses anyway. So, even if they improve the focus system - they need the 300mm, 400mm and 500mm lenses to compete with Canon & Nikon. Otherwise, even if they could get their focus system up, the sports and wildlife shooters would still choose canon/nikon because you need the lenses. If you build the lenses and the focus system doesn't hold up - people will still choose canon/nikon. So pentax has to do BOTH And at the same time.
AND, even if pentax does get an aps-c solution or full frame solution - all that will do is drive canon/nikon to respond. The easiest way to respond is to bring advancements to market sooner.
So, to really get to your idea - pentax needs something completely unique - not just something like what the competition has. When it's a 2-man race you can keep things throttled back (like we see with Canon/nikon at the higher end). Once you get to 3 players then we see change in reducing the time-to-market of new models.
