I finished (not beat) the game last night and two words apply, gutted and unfulfilled.
The endings that are currently there are just place holders for the real endings. This is most likely being done in an attempt to combat piracy because the real ones will be DLC requiring an Origin account etc.
There is another theory going about that since Japan players won't see the game until the 15th March, the real endings are being held back to allow everyone to experience it at the same time.
If I'm correct and this is the case then the DLC would need to come very soon and need to be very free. Trying to charge people to get the real endings would be an extremely cynical and transparent attempt at creating revenue and in the long run will break Bioware in two. Gamers will not be milked like cattle to increase the baseline profits of the company.
In regard to the Galaxy at War nonsense, there is a slight difference in one of the current endings that you can only see, in game, if you have played this and raised your readiness to a certain level. Now, based on the statement made that Galaxy at War being optional and not required, the current evidence implies you may have to use it to get an ending you want in the single player only environment. I hope that in the DLC for the real endings, the galaxy at war requirement they currently have in the game is resolved so that all endings (bar maybe one special one for people who do invest the time in the multiplayer) are available to me.
I'm no Bioware fanboi, Jade Empire was an atrocity that cost me 20 odd hours of my life that I'll never see again, so trying to get the goose to lay another golden egg in order to download what I should have been given in the box, and should be able to see without paying for XBox Live membership \ doing something I hate (multiplayer gaming), will make me think twice about buying from them again.
If all above is right, then Bioware are trying something very brave and if they pull it off, then they deserve to be commended. I fear though they will try to be too smart and end up doing something stupid. If so then it's going to come back and bite them hard.
I read around a few boards last night after getting depressed at the let down of the current endings and there are more than a few people who are out for blood over this.