Ken Levine calls fallout an "important moment" for industry, says fans will be "very disappointed" if BioWare decides to write new ending.

[Khuutra]

Soundwave said:

Why not just let the fanbase write the entire story then? Why just stop at the ending? 

That's just it: they did. That's how they sold Mass Effect, as a story that was written as a collaboration between the development teams and the fans.

What BioWare is doing here is rendering a service, like Doyle did when he brought Holmes back from the dead (after which all the best Sherlock stories were written, I'll point out). There is nothing inherently wrong with admitting that you are not the sole owner and proprietor of your product.