Apple iPhone 4S jailbreak has places to go and people to see, unlocking would be tougher
The good news is that it shouldn't be long before a jailbreak appears, since the Chronic Dev Team recently announced they've found no less than five software bootrom exploits for the A5 chip inside the iPhone 4S, and are saving them for the release. The iPad 2 jailbreak came comparatively late, since it was hard to get access to the bootrom, placed inside the A5 this time. Since then, however, these five userland software defficiencies uncovered mean that Apple shouldn't have plugged the flaws with a revised hardware.
They should be good for iOS 5, which was done and dusted hours after the first beta release, and four more software revisions, but if this is not enough for you, Geohot had mentioned that he has another hardware exploit like the Limera1n saved, which could possibly jailbreak the device once and for all, without the need to do it after each update. So, unless Cupertino's engineers have taken some extra special precautions, we should be runnung Cydia on the iPhone 4S in no time.
Since there will be a SIM card slot for getting on GSM networks like AT&T, unlocking here should be relatively easy, but with the combined GSM/CDMA baseband radio chip from Qualcomm we are in uncharted territory even regarding the GSM unlock, so we'll have to wait and see what the modders can do to make your iPhone 4S a true "world phone".
On the CDMA side of things, it is rather different. As CDMA phones don't use SIM cards to identify to the network, you can't just swap another carrier's SIM. That's why the CDMA receiver is not locked at all. However, the carrier has to activate the unique MEID number of your handset so you can use it. Since the iPhone 4S phones from different carriers will be 100% identical technically, registering them on another CDMA network shouldn't be an issue. However, although we wish carriers will activate any iPhone 4S, it is very likely that they will activate only the ones bought from them. For example, Verizon will activate only iPhone 4S handsets bought from Verizon or its distributors, and not ones sold by Sprint, AT&T or any other carrier in the world.