http://www.apple.com/feedback/iphone.html
However, a couple of points:
- Siri will almost certainly not be added to iOS devices that do not have it presently, since they lack the hardware to support Siri.
- I don't understand what you mean by "retina display update". Perhaps if you clarify, someone can offer advice. You'll certainly want to clarify your point if you submit feedback to Apple.
- the same applies to "Launch Pad". I don't know what you're referring to, unless you're referring to LaunchPad in Mac OS X 10.7 and 10.8, in which case you have basically that same function in the Home Screens on the iPad now; indeed, LaunchPad is basically the Home Screens copied, as closely as applicable, to Macs.
Regards.