It seems that invitees to Google's big not-yet-officially-about-Google-Music-event have just received a second invitation - to the after party. Oh, and Maroon 5, Busta Rhymes, Dirty South, R3hab, and Drake will all be in attendance - and so will we.  We'll be watching the earlier event via livestream along with most everyone else (space is apparently very limited), but Android Police will present for the post-event-event Wednesday night, below. We're excited.

But as awesome as the event's headliners are, we're still more interested in what it is Google and T-Mobile are launching that warrants such a high-profile promotion.

Now, we don't have any inside information regarding what's going to be going down on Wednesday in Los Angeles, but I think I might have a pretty good idea - so, humor me for a minute.

Given that the event is clearly focused around music (per the "These Go To Eleven" invitation we saw earlier last week and the musical guest list above), we think it's very safe to say that Google is planning on making an announcement related to its much-awaited Google Music storefront product.

The leaked screenshots of what is purported to be the Google Music Store are also clear evidence (if genuine, and we're pretty confident they are) that Google has been hard at work getting a store front ready for launch, and it looks pretty polished at this point to our eyes. This would indicate that a product launch is definitely close.

Finally, there was the inside story on Google Music's song-sharing model last month, leaked by a music industry insider who claimed that Google and the major labels had finally reached a distribution deal.

All signs point to the launch of the Google Music storefront being imminent. But where does T-Mobile come in? I've got a few ideas, and I'll list them from what I think is most to least likely:

  1. Unlimited Google Music streaming for T-Mobile customers: This, in my mind, is the most probable outcome of Wednesday's event. Given Google and T-Mobile's historic relationship with the Nexus line of phones (and the original G1), the two companies have clearly had some big product partnerships in the past. An agreement to allow T-Mobile smartphone customers to stream from Google Music without using any of their plan's data "bucket" would be an obvious way to promote Google's Music store over competing services, and would likely be coupled with a carrier billing option for those purchases. Combined with T-Mobile's 4G, the two could advertise that they stream the highest quality audio possible at the lowest cost - perhaps even giving Google Music streaming preferred bandwidth access (I wouldn't bet on that last part).
  2. Special Google Music subscription service for T-Mobile customers: This seems less likely in light of the insider rumor that Google Music will not be based on a streaming subscription access model, but rather an MP3 storefront with social song sharing. However, it's possible that Google has licensed the rights to its entire music library to T-Mobile (this is unlikely given that Google's distribution agreement with the record companies probably forbids this sort of thing), and that T-Mobile customers will be able to pay a very competitive monthly fee to access this library. This could be in conjunction with the above unlimited streaming idea.
  3. Galaxy Nexus For T-Mobile And Google Music Store Credit: This is definitely possible, but it seems less likely than my first suggestion. There have been no signs of a GSM version of the Galaxy Nexus hitting the FCC yet, though obviously European versions will be packing such radios, and FCC filings can be obfuscated and temporarily hidden from public view at the request of the filing party (Edit: Whoops, guess there has been a GSM Galaxy Nexus at the FCC - my bad.) Given that T-Mobile has been the official Nexus handset launch partner in the US historically, we wouldn't put this rumor completely out of contention. T-Mobile customers buying the Galaxy Nexus could get a nice big Google Music gift card of sorts - and again, this could just as easily be coupled with my first suggestion.
  4. Google Buying T-Mobile Instead Of AT&T: This is very, very unlikely, but given that AT&T has faced a lot of scrutiny over its decision to purchase T-Mobile, we wouldn't say it's impossible. File this under the "in our dreams" category. The heavy focus on the music theme of the event also make this seem even more improbable as a venue for such a serious announcement.

What do you think is going down on Wednesday? Let us know in the comments.