This silence could be also taken as to "Wait for the perfect time to announce the ending.". The outcome will be biggest if the outrage is the loudest.
Now, Bioware is not stupid. They are a big company, they are not 3 people sitting in a basement. I think they KNOW:
"Either we change it, we add something, or we loose millions of dollars every year.". With EA beeing a sponsor, I can see a great deal in EA demanding Bioware to release the ending in a DLC which EVERYONE will buy just to get more money. If you have invested hundreds of hours, you want a worthy end. And who here would not pay for it?
With the pressure going on now, no company would keep quite over such a long time if there was not a A+ backup plan in stock.
"Why not go into detail now? Everyone knows the endings.". Yes, but not everyone actually has this emotional state we have right now. We WANT it to end, no matter what the price. Others maybe not. So wait until more complete the game, and then release it. We are in this for the long haul. They know, one week more or less won't kill everything.
The refund thing is actually not by Bioware, but by some companies themselves. When I was in a Media Markt today and asked about it they said: "No, No refunds.". If Bioware would want to get rid of us, the order for refunds would be everywhere, not just amazon and Origin. It is simply a matter of saying: "If you are not happy, we will refund you.". It is to keep bad critics because of wasted money at bay. It would also contradict with gambles post: "If fans knew what is to come, the reaction would be different.". He is NOT a fool. He knows that the only different reaction (Happiness) would be a new ending.