OK, your going to have to explain the rational behind your disappointment. Are you normally disappointed when things get upgraded?
Sure, I'll explain. It's not actually an upgrade.
All other things being equal adding megapixels gives you the following advantages:
1. You can make larger prints
2. You can crop tighter
HOWEVER:
There are limitations with the lens and sensor. Putting more MP on the same sized sensor creates higher pixel density. We are at a saturation point with the current 5MP sensor where adding pixels will add substantial noise and therefore degrade the image quality. 8 MP on the current sensor is a downgrade. At best, coupled with in-camera processing algorithms to deal with the noise, it's a lateral move. It requires concessions to be made.
You can't simply stick in a bigger sensor, either. You are limited by the focal length, which is dictated by the thickness of the device. Adding a DSLR-sized sensor to deal with noise requires the attachment of a DSLR sized lens. There is no magic way around this.
Focal Length:
http://www.dpreview.com/learn/?/Glos..._Length_01.htm
To those that want even more MP. You have to ask yourselves; what's the biggest print you've ever made with your iPhone and do you plan to do that with any regularity? I'm betting the answer will be "small prints" or "none at all". So, no advantage realized with the downside of more noise.
Here is another way of looking at it. Imagine if we're talking about stereo amplifiers. You have one with 1000 watts of power (which you rarely use to potential) and, for the sake of numbers, you want an "upgrade" to 2000 watts of power. However, you'll have to deal with more distortion at ALL listening levels. Do you really want that? "More" is a downgrade.
So I'll take the perfectly good pictures of the current camera. Who really wants larger file sizes without any substantial benefit?