The Apple rumor mill is reaching a fevered pitch in advance of Wednesday’s event, where the company has invited press to “view our latest creation.” It’s not an upgrade to an existing product, not a new service announcement - but an actual new-never-before-seen-or-touched shiny sleek piece of tech. Given the impact that past Apple products have had on the music industry, Billboard rounded up the most persistent rumors, rated how likely they are to come to pass, and analyzed what each would mean for the music industry.

Tablet (Likelihood: Extremely High)
At this point predicting that Apple will release its long-rumored tablet computer falls into the “duh” category - it’s a near certainty. It’s expected to be a bigger version of the iPod Touch. Think a big touchscreen device with no keyboard and connects to both Internet and home networks via WiFi. How much? Apple blog 9to5 Mac says it will be under $1000. The lingering questions revolve around what the tablet will exactly do and which, if any, of these capabilities will matter to the music industry. Some scenarios:

E-Reader (Likelihood: Extremely High)
It seems likely to impact the publishing business first, as an Apple tablet would be aimed at Amazon’s Kindle and be used to download books, newspapers and periodicals. If it revives the publishing business and becomes the default player of choice – like the iPod did in the music business - there are some interesting music industry benefits. Think reading a music review and including one-click links to buying or streaming music, not to mention links to music videos, live concerts, and any other music-related topic so many periodicals discuss today. If a picture is worth a thousand words, what’s a music stream or video worth?

Universal Remote (Likelihood: Medium)
Should a tablet indeed emerge, it is likely that it will act as some sort of universal remote for all the digital content in the home. It could connect to both the broader Internet as well as a local area network to find and aggregate content stored on multiple computers, iPods and stream it all via the TV or any other connected device. Of course that will likely require that all such connected devices are also Apple products, given the companies closed ecosystem philosophy. While that’s likely not a problem to the many who own Macs, iPhones and iPods - the Apple TV is a flop that few use for their connected TV needs. It’s hard to see a tablet being so useful that it will drive sales of the compatible Apple TV.

Apps, Apps, Apps (Likelihood: High)
The software powering the tablet is expected to be a beefed-up version of what currently runs the iPhone, and a tablet that’s just a bigger version of the iPhone will likely carry with it bigger versions of iPhone apps. Think more apps, that do more and cost more. Many of those will almost certainly be music related—either simple tablet versions of existing iPhone music apps, or more sophisticated versions that take advantages of the tablet’s expanded functionality.

New iTunes: (Likelihood: Low)
Yes, Apple bought streaming music service Lala last year. And yes, Apple just recently began touching base with the labels by phone to provide some early guidance on its plans for that service. But sources say that plan remains in the preliminary stages and no in-person meetings have yet taken place (nor are they expected to for at least a number of weeks). So don’t expect the Apple to unveil the Web-based version of the new iTunes at this week’s event.

That’s not to say the tablet won’t someday play a role in whatever new iTunes eventually launches. The rumor back when Apple introduced the iTunes LP initiative was that the program would find its true potential on a tablet-like device. Should the labels and Apple create enough iTunes LP content, it’s possible that Apple could add a special section for the digital albums in either the iTunes Store or as a category in the App Store.

Aside from the tablet news, other details to expect from Wednesday’s event include:

iPhone software update: (Likelihood: Somewhat High)
Since the new tablet is expected to run on an improved version of the iPhone OS, it’s not a stretch to expect some of those improvements will find their way onto the iPhone as well. And while the tablet news will likely dominate the day, the importance of a new iPhone operating system should not be overlooked.

The last significant upgrade to the iPhone OS added in-app commerce capabilities, which opened new doors to music applications like TapTap Revenge 3 and I Am T Pain. Both games let users buy and download new songs for 99-cents each, and report healthy activity on that front (2 million for TapTap Revenge 3 and 350,00 for I Am T- Pain).

Something sorely missing from the iPhone experience to date is the ability to run background apps. iPhone rivals Android and BlackBerry allow this, and make it a point of differentiation. If Apple finally allows the running of background apps, expect a notable uptick in the usage of streaming music services as users play music in the background with interacting with the phone’s other features.

One More Thing (Likelihood: Unknown)
Jobs loves to pull a last little rabbit out of his hat at the end of his presentations. This time it could very well be an announcement that the iPhone will become available through another U.S. wireless operator, likely Verizon Wireless.

Piper Jaffray analyst Gene Munster puts the odds on Verizon adding the iPhone this year at 75%. Between that and the predictions that Apple will introduce a new iPhone this June, it would make sense to introduce the Verizon deal now. Anytime an operator adds a phone to their network it has to go through FCC approval and those records are public. The minute Verizon applies for the iPhone, the news will break everywhere; announcing plans to do so at this event will let Apple bask in the glory of making the announcement.

Check in to on Wednesday for live reports from our correspondents on the ground in San Francisco, followed by analysis after the news conference.