Whether or not Apple gives it the version number 10 mentioned in roadmap documents, and whether or not it has all of the features we’ve seen in early betas of iTunes 10, a new release of the company’s content-delivery-and-management software is as much a certainty is anything can be for a rumormonger in the lead-up to such an event with its docket under the ultimate control of such a small handful of people.

Although many of iTunes 10′s features have been clearly targeted at the company’s forthcoming Tablet computer/device, and a stripped-down feature set could be carried over into an interim release of iTunes 9 without compromising much of the functionality relevant to existing Macs/iPhones/iPods, the prevailing consensus on the grapevine seems to be that many ostensibly Tablet-specific features — like “e-reader” content delivery — will be available right away on existing Apple products and Windows PCs. The murky trend of “grapevine consensus” notwithstanding, we tend to agree based on all available information just hours before the Event begins.

The iTunes 10 (often referred to as iTunes X, though that label has been lurking around inside of iTunes’ code for several versions now) feature set, as of our last glimpse at development in the late alpha/early beta stage, included:

• Support for new streaming audio and video subscriptions
• Improved “social” (Facebook, Twitter, etc) features
• A number of tweaks to Home Sharing, ostensibly to better support the full capabilities of the Tablet since few changes were visible in our testing with Macs
• An overhaul of the iTunes Store to support new content including streaming options and media for the tablet’s new e-reader functionality, with similar functionality available across Apple’s entire hardware lineup.
• New Sync functionality for the Tablet, including wireless sync via Bluetooth and 802.11n Wi-Fi, which will carry over to at least some degree for the handheld iDevices despite their lack of support (in software, at least, for the latest iPod Touch which does have an 802.11n-capable chipset that Apple has chosen not to fully enable) for the much faster 802.11n wireless networking standard. Bluetooth Sync almost certainly be subject to some limitations, such as only exchanging lightweight text data such as Contacts, Calendars, Notes, Safari Bookmarks et cetera.
• A primary goal of iTunes 10/X outlined in internal Apple documents early in its development, was similar to that of QuickTime X — maximum integration with new Snow Leopard-era core technologies, a Cocoa core to replace its aging Carbon heart, and 64-bit support. There has been some question as to whether all of those goals were in fact fulfilled (several planned features have been held back for future release), but at our last opportunity to get our hands on a developmental build, iTunes 10.0 ran as a 64-bit application on Snow Leopard with significantly improved general performance over version 9.

Apple will no doubt surprise us with other features, and could easily hold back any number of these things in favor of a simpler interim update to iTunes 9, but that’s what we have come to expect from version 10. Whether 10.0 as we know it will be made available for download on Wednesday or not remains to be seen.

As for iTunes the service, streaming and subscription-based payment models (for at least some forms of content) have been widely anticipated. It’s well-known to insiders that Apple is working on reducing the cost of video content — particularly television shows — to increase its appeal for customers who can get many of the same episodes on ad-supported free services such as Hulu, but so far our sources in Cupertino say that Apple’s efforts in that area have been largely frustrated by a TV industry desperate to avoid deflation of any of its revenue streams.

Given the surprising popularity of e-reader software, notably Kindle.ipa, on the iPhone platform….we anticipate that Apple’s e-reader services will be rolled out as quickly as possible; even if that isn’t immediate. We have reason to hope that it will be, however, given how much work Infinite Loop has put into this and how eager its content partners are to get started.

Stay tuned for more Previews, and be sure to check out our Live Coverage/Discussion of the January 27th Apple Event starting at 12:45 PM Eastern/9:45 AM Pacific right here: http://macosrumors.com/2010/01/27/tablet-event-live/ or follow the live broadcast posts without discussion on Twitter: @MacOSRumors.