I hate to say it but I think you're going to be waiting a long while for an sd expansion slot on an iPad. NFC- on an iPad? I don't see the use. iPhone I get, for sure, but not really for the iPad. Yes, Siri would have been nice but I'm positive that could be addressed with a software update.
Anyways, the iPad 2 is still one hell of a device so as long as you're happy with it; that's really all that matters!
Eventually the iPad will get Siri it's only logical. I question if Siri's server is not ready for the increased load. It seems to be possible to run Siri on a jailbroken iPhone 4 so does it seem logical that Apple is limiting Siri to the iPhone 4S until the server is efficient enough to handle the demand?