nono, the original ending was still that sinclair becomes valen, it just happens at the end of the series instead of a side story. that's why o'hare had to come back and wrap that up - it was an essential part of the story after they did all the set up in season 1, with him lighting up the triluminary after being captured by the minbari at the end of the earth/minbari war. think about how sheridan's story ended - he also vanished in a flash of light never to be seen again. just replace his story with sinclair/valen.