I'd avoid the iPhone 4 at all costs. It's a horrible phone (as in telephone to make calls) my iPhone 4s is truly an excellent phone, where in many places my iPhone 4 wouldn't even connect.
For the price difference an iPhone 4S is vastly superior.
As far as timing, you've made it this long, wait until at least two weeks after iPhone 5 is released, then find the best price on an iPhone 4S & buy it.
LOL, the same could be said with the 4S considering that the battery life issue has still be resolved from Apple the last time I checked. I actually like my iPhone to make it through a day of decent to heavy use and still have a charge when I get home at night. Typically, the dropped calls do not result from the iphone itself but from the lack of coverage or crappy coverage that AT&T has for their network. Which is the main reason I am switching to Verizon. My iPhone 4 works just fine for a phone. Infact it is the only phone I have and has served it's purpose well for the last two years since I bought it in June of 2010. And while I still only get about 1 bar of service in my house I can amazingly make and receive calls with pretty much no issue. I occationally get the Searching or No Service message but that is not the phone's issue, that is AT&T's issue. As for the iphone 4 dropping $50-100 in price, that might be the case if you are getting it from Verizon or AT&T but that is if you sign up for a 2 yr contract with them. Otherwise if you want to buy it outright from them you are still going to pay close to full cost of the phone which will still be more than $200.
Hell, If I didn't want to get rid of AT&T I would still be rocking the 4 probably until the iPhone 5S or 6 comes out since it runs just fine. I keep a case on it all times so it is in pretty good condition. I won't say mint since except for some minor scratches from the snapon case that I use on the metal antennae band around the edge I would say it was in very good condition. I try to take care of my apple devices.
I won't dispute that the 4S does have better technology in it than the 4. It should since it is a newer model. Otherwise there would be no point for people to upgrade. Siri would be nice (as long as she works the way she should). The 8MP camera is definitely a nice upgrade over the 5MP in the iphone 4 (this is one thing i am looking forward to in the iPhone 5). The ability to use AT&T's HSPA+ network for faster 3G/4G speeds is nice as well. The A5 chip instead of the A4.
And the ability to get I believe full support for iOS 6 when it is released instead of the chopped down version for the iPhone 4. But to tell you the truth, when I saw the preview of iOS 6 I wasn't super impressed with it. I think I was more impressed with iOS 5. So Siri gets to report sports scores now. Wow! Could care less. I want Siri to be my personnal assistant with appointments, alarms, text, emails, phone calls, opening apps, updating contact info, etc... and flawlessly. I don't want to get frustrated with Siri and say screw it and then open the app my self to set an alarm or create a calendar event, or update a contacts info. What is the point of having Siri then. Yes I know it is in Beta at the moment so we will have to live with the issues.
Facebook integration.......snore......I don't use facebook. I don't Twitter. So those are useless options for me.
I am interested to see how Passbook will work though and see if it will be revolutionary.
Facebook over 3G/4G......I could Skype before over 3G/4G and it is cross functional with more than just Apple devices (Android, laptops, desktops, tablets, etc...) I only Facetime with my wife and daughter when I am away from home. Otherwise it is normally Skype that I use. Plus My3G allowed me to use Facetime over 3G on my iPhone 4 and iPad 3 anyway.
The phone options now are definitely nice since I have a lot of meetings to go to. That I think is probably the biggest new option in iOS 6 for me.
Mail........meh. The current one gets the job done for what I do and there are JB tweaks that make it better anyway.
Safari. Shared tabs like in Chrome (which still doesn't work right on my iphone and ipad, constantly freezes up, the app, not the phone). If this works on my PC with Safari installed and my iphone/ipad, then I like it. If it only works on Macs and iOS devices, I don't care then since I am not dumping money on a Mac anytime soon.
That is pretty much the major stuff though that they announced. I want my JB tweaks to finally be incorporated into iOS. IntelliscreenX calendar and message reply. Toggles to be in the notification center to turn on/off Wifi, BT, Data, etc... A built in Ad blocker in Safari so I don't have to download a tweak for it (and no, I do not prefer any of the other browsers in the App Store over Safari. Safari seems to run the fastest out of all them so that is what I stick with).