From wikipedia:
To what was posted in the media, the film was cut by the studio quite a bit earlier than it may have seemed. This meant that visuals were not all completed to a sufficient and presentable standard. To finish the visual effects on Weitz version of the film may prove to be prohibitively expensive. He's going to be handing in a version of the film and a budget to the studio; but he would be surprised if they agree to fund it. And they still hold the rights to the film, so that would be the only way a version would be completed.
That also includes the ending, because Weitz still intends to add to his version when there are no sequels.