A few things first:
1) I don't have anything against Pentax gear. I think it's very competitive with the other equipment in its price range.
2) My comments don't really apply to casual photogs. I'm really only making these statements for those people that think they will get serious about photography. If it will become your profession or your passion, you'll probably be making a greater investment and you need to be more cautious about it.
3) Regardless of what equipment you buy, it still pales in comparison with the skill and knowledge of the photographer. Lack of skill is far more limiting than lack of equipment. Whatever brand you use, learn to use it well.
1) I don't think there's any danger of Pentax disappearing any time soon. They've been around for decades and their current DSLRs and lenses are highly regarded and selling like mad. They are a smaller company and are not attempting to match the volumes that C/N move. They're making a lot of money off their DSLRs, plus they have investments from Samsung (which is not exactly a small company) and Hoya.
It doesn't take a large share of a market in order to remain healthy. Hey, look at how few cameras Hasselblad sells, too!
I suppose I'm sensitive about camera system orphaning because I've seen it happen to several people. If you look at the transition from film to digital, here's the rough chronology (as I remember it):
In 2000, Nikon released the D1 and Canon released the D30. They weren't cheap ($5K and $3K respectively), but they started a revolution. No word from Minolta. Pentax announced the MZ-D. Pentax was never able to turn it into a sellable camera.
In 2001, Nikon introduced the D1x and Canon introduced the 1D. No word from Minolta.
In 2002, Canon introduced the D60 and the 1Ds and Nikon introduced the D100. The major brands not only had distinct model lines of DSLRs, but no word from Minolta. In fact, Minolta wasn't even discussing plans for a DSLR.
In 2003, Canon rocked the market with the first sub-$1,000 DSLR. They also introduced the 10D. Nikon introduced the D2H.
By then, the Minolta photography fans that I knew threw in the towel. All of my Canon and Nikon friends had converted to digital. Some were on their second bodies already. The Minolta guys couldn't take it and dumped their gear at horrible losses.
It was that year (I think), that Pentax introduced their first digital camera. I never met anyone with one, but at least they had something.
After that, Konica bought Minolta. Minolta announced a DSLR (or maybe two) but got no traction in the marketplace. They finally dumped their camera division and sold it off to Sony.
Sony appears to be applying all of their recent magic and has shown as much success with DSLRs as they have with MP3 players, laptop batteries, and the PS3.
To recap, in 2000 there were four major camera companies for serious shooters (not including the niche brands in the medium to large format space). They were Nikon, Canon, Minolta, and Pentax. Within 4 years, Minolta was essentially dead and delays in Pentax getting into the market had sunk it to niche player status.
In my real job, I'm a manager in an IT organization. One of the things we do whenever we invest in new software is guage the financial strength and commitment of the vendor. If I applied the same process to Pentax, I'd walk away nervous. I wouldn't cut them from the list, but it would be a significant knock against them when comparing them to other companies.
From 2004 to 2005, Pentax saw their profit decline from 6.9 billion yen to 3.6 billion yen. Their Life Care division went form a 6.1 billion yen profit to a 3.5 billion yen profit. Their Imaging System division (cameras, lenses, binoculars, and telescopes) went from a 1.2 billion yen profit to a 2.8 billion yen loss.
In 2005, Pentax partnered with Samsung to get some badly needed help with digital imaging systems. That certainly gave Pentax fans hope that the company could survive in the rapidly evolving digital SLR space.
In 2006, the Imaging System division again posted a large loss (1.2 billion yen). Later that year, Hoya purchased Pentax. Despite having a less well known name, Hoya had double the sales of Pentax and 20-30 times the net income. In the press release announcing the deal, the Imaging System division was listed last among the five division. Hoya's CEO made his priorities plain when he said ""The most attractive part about Pentax was its medical business."
Here's what Hoya Pentax's press release had to say about the Imaging System division:
"Imaging systems area: (Major products include: digital cameras, binoculars, etc.) In order to enhance business value, the new company will differentiate its offerings by specializing in high-value added products with unique technology and will focus on areas where it has a competitive edge. This area will be positioned as a foundation for development of new optical-related equipment and is expected to diversify into the life care and security business areas."
That's hardly a ringing endorsement of a strategy to hold a small position in the consumer DSLR market.
Will Pentax make it? Probably, but it is definitely a much greater risk than Nikon or Canon. I'd say that the big two will almost certainly still be cranking out new cameras in 10 years. I'd give Pentax a 2 in 3 chance of doing so (although I'm not even close to being an expert in this area). If I was starting from scratch and was planning on making a major investment in equipment over the next several years, I'd definitely take that risk into account. If I was having any trouble (without factoring in brand health) between Pentax and either Canon or Nikon, I'd definitely go with one of the more successful brands.
Sure, it's a bit of FUD. However, it's honest FUD. and FUD is a reality in any technology business that involves a significant commitment.