Because the run-up to Christmas is the biggest buying season for cameras, this is usually when we get the most questions along the lines of "how long will this camera last?" and "is DX/FX a good investment?" or "will prices come down any time soon?" or "will this model be replaced soon?"
Let me tackle those in reverse order:
- "Will this model be replaced soon?" Unless the model you're referring to was just released the answer is yes. Compact cameras are on one year cycles now, DSLRs are on 18-36 month cycles, depending upon the model. Cameras are now no different than autos, refrigerators, computers, or iPods: they go through regular refreshings, some modest, some major. There's no end in sight for adding more image quality, but each generation now tends to have less discernable gains, especially for Web or casual print work.
- "Is DX (or FX) a good investment?" No. Cameras are not good investments. They are purpose built tools (and narrow purpose at that). Like autos, refrigerators, computers, or iPods, they decline in value the minute you buy one, and the eventual decline can be quite high if you pick poorly.
- "Will prices come down any time soon?" I'm tempted to jump into an economics lecture, but I'll try to keep my answer short: probably not. Certainly here in the US the most likely economic scenario says that all imports are going to get more expensive. The question then becomes whether the manufacturers can remove cost fast enough to counter that trend. To some degree, yes, but the rise of other economies (e.g. China, India, Brazil, et. al) give them an out: they can simply target other markets more heavily. The trend with the type of Nikon equipment this site mostly deals with is that prices have risen slightly in absolute dollar terms. There's nothing I know of that's likely to change that any time soon. However, we've been through big yen/dollar pricing waves before, and it's the old "what goes up must come down" thing. Unfortunately, that tends to happen over decades, not months.
- "How long with the camera last?" Compacts aren't built to rugged standards, even the high-end models. Abuse them and they'll become paperweights within a year or two. Handle them with care and they'll last longer. But they have a couple of strong points of failures: lens extension seems to be the most common death symptom, and it's happened to about half of the compacts I've used over the years that have extending lenses. Unfortunately, the cost of repair is greater than replacement. DSLRs tend to be built more rugged, but they don't survive drops and being flung into solid surfaces via a swinging neckstrap. Rough handling can lead to subtle issues (lens mount misalignment, for instance), but it's a lot tougher to kill a DSLR. The most common death syndrome I've seen is electronics: some component on a board in the camera dies and now the whole camera is (mostly) inoperative. Cameras without weather sealing exposed to high humidity, sea salt, and other pernicious threats to electronics are more vulnerable, but I've seen pro cameras succumb, too. Depending upon initial cost, it may or may not be worth repairing such camera failures. Right now that cut-off seems to be about up to the D70 generation (i.e. you could buy a used D70 for the average price it costs to repair most failures). So, my answer tends to be: two years for compacts, five years for consumer DSLRs, longer for pro DSLRs.
That said, there's another aspect to most of those questions that needs to be contemplated. Even non-photography sites have finally caught onto the trend I've been harping on for some time: the days of the traditional camera as a mass market item are numbered. Apple, once again, has shown the way, and the Japanese companies, once again, have totally missed the turn. Heck, they might not even have a steering wheel.
The iPhone has proven to be the most flexible camera out there. It's connected, it's programmable, and it integrates into a user's workflow very easily. Not that companies like Nikon haven't tried bits and pieces of Apple's strategy. The Coolpix P6000 had a built in Ethernet port that enabled connectivity. To one thing: Nikon's myPicturetown. Not Facebook. Not Twitter. Not email. Not anything any large group of users would want. And Ethernet? Too clumsy. It requires a cable in these days of wireless.
Unfortunately, the Japanese companies tend to take the wrong messages away from failures like the P6000. The P7000 has...no connectivity at all!
So, if you think you're buying a camera for the long term, you might not be. I'll bet that the majority of photos taken five years from now will be taken on "connected cameras." Whether that's a cellphone with camera or a camera with bluetooth/WiFi is uncertain at the moment, but the longer the Japanese camera companies ignore the trend, the more likely it will be the former and not the latter. We can put larger sensors in cellphones that don't get much larger than the current models. Maybe not FX sensors ;~). But certainly larger, more capable sensors that'll give you 10mp or more with reasonable performance at ISO 800 and probably higher. And those won't require a computer as workflow intermediary.
Buy what you want or need this Christmas season, but don't fool yourself into thinking this will be your photographic solution for the next decade. It won't.