I think I will just wait for the official release.
Do you know if updating saves app data? When I restored to jailbreak all the apps I backed up had the same saved data on them but I wasn't sure if they save if you upgrade from iOS5 to 6 because it's a major upgrade
Back-ups should save all local app data, in fact, you can even toggle which apps you want to save the data from in Settings if you back up to iCloud. However, if this isn't enough for you, you can always install a tweak that manually backs up save data, like DataDeposit, which backs up individual app data to your personal Dropbox. If you don't have a Dropbox account, you can make a 2 GB one for free, which should be more than enough to back-up all your save data.
iOS 6 will be jailbreakable (tethered) on all devices with an A4 or earlier processor (iPod Touch 4G included) due to a bootrom-level exploit (limera1n) that cannot be patched. Chances are there will be GUI applications (redsn0w, sn0wbreeze) that will jailbreak it literally the day it goes public, as the Gold Master is already jailbreakable and that's the exact firmware that will be re-labeled and released to the public. No estimate of when the jailbreak will be untethered, though. Untethering requires a series of other exploits that devs don't make public until they've been patched, and don't even talk about until a week or so before they've been implemented. [An exception to this is the iPhone 3GS with the old bootrom. It is vulnerable to an exploit that can jailbreak and untether it on every firmware]
Siri will not be available on iOS 6 for any older devices. I'm going to rant a bit here, so you can skip this paragraph. Apple is extremely greedy. They imply that Siri cannot be implemented on older devices, but they never outright say it, and they never give any technical reasons. They just gloss over it and get louder about how great it is (I have it on my 4S and I promise you, it's really not that great, and you'll probably very rarely use it) and how it works so well on all the new devices. Well, numerous jailbreak devs have released ways to get Siri onto older devices, like Spire, which was an absolutely perfect implementation that worked only on iOS 5.0.1, and Spite, which was a little less reliable, but still worked well and on all firmwares. There are others, but I won't go into it, the point is that it's been proven over and over that not only does Siri work on pretty much every iDevice, it works extremely well. This leads me the the logical conclusion that the sole reason Apple does not put Siri on all devices is solely to goad consumers into buying newer products. It really wouldn't even make me that mad if it weren't for the fact that Siri isn't even that great, but they're using it as the main selling point for the 4S and a major selling point for the iPad 3. It's lazy marketing, and it's sad because it works so well, and it sets a precedent for Apple that they really don't even have to do great things with each new revision. They just have to slap some gimmick on it, advertise it, and throw simplistic ads about. This attitude makes it so that Apple doesn't need to make great new innovations or quality improvements with new products. They just have to buff the old one a little. It slows the advancement of the entire brand, but I think that's enough ranting for this thread. It's stupidly off-topic.
One last thing, I'd like you do to a little research and decide if iOS 6 is even worth updating to at all. It really doesn't offer many improvements of iOS 6, esecially if you aren't using an iPhone 4S or iPad 3. In fact, it even detracts from iOS 5 in some areas, like ditching Google Maps in the native Map app, and throwing out the native YouTube app entirely (which, to be fair, wasn't that great, anyways). The improvements are very minor and are all preemptively obsoleted by various jailbreak tweaks or even apps already in the store. If anything, you should at least wait before updating to see if there any reports of memory leaks or inconsistent battery life issues before you update. iOS has a bad history with battery issues on fresh firmware releases. Finally, keep in mind that with each new iOS revision, the amount of memory and CPU required to simply run the device increases, so if iOS 6 is too much for your device, even though it's supported, your device might suffer from a lot of slow-downs. I get some of that on my iPad 1 on 5.1.1, but it's vary scarce and a good amount of it is probably due to certain jailbreak tweaks I have installed (but FolderEnhancer is just too good to not use).
I hope this post has informed you thoroughly, and if it hasn't, at least given you the drive to look into this for yourself. I won't blatantly tell you to google it, but it's your iPod, you should at least know a bit about it and its future, especially if you're a jailbreaker.