The real advantage that they have is that you always have them. You don't have to debate whether or not to take them or make sure you remember to grab it. You just have it.
The downside is the picture quality is fairly poor and I don't see that changing a whole lot. The sensor is just too small, and if you make it bigger, then it and the lens take up more space and add weight, both of which are at a premium on phones.
In the next five years I predict:
- the pointless megapixel race will continue 2MP now, probably 4 or 5 in five years. Mostly useless over 2MP and totally useless over 3MP, the quality just isn't there, even in bright light.
- LED flashes: This will help things a little. More and more phones will get white LED flashes on the camera. They will actually help a lot of shots where camera phones are used, a group of friends taking a picture from a few feed away, like at a party or sitting around a table at a restaurant. As a bonus, they can be used as a flashlight.
- Video: They currently have pathetic video (mine does something like 176x144 at 10 frames a second). This will get better, but who knows how much. I think in 5 years, most phones will be doing 320x240 30fps and high end ones will do 640x480 @ 30fps.
- Phones with real cameras will remain a small niche. There are a couple of them now, with real flashes and zoom lenses. Here's the problem. The bigger camera parts add weight and bulk, and you have to carry them around all the time, even when you don't need the camera. Better to have a smaller, not as good camera with you all the time for those spur of the moment things and bring a point and shoot when you know there will be photo ops. There are some people who carry a point and shoot everywhere, and a camera like this would be an advantage for them, but I doubt that is a huge market segment.