I went to the public forums before the official design plans were unveiled in 2007 and the plans by the city were that 1200' could be the maximum height to the roof, or perhaps opaque crown, but that spires could extend much further, perhaps to the 1375' proposed by SOM, or maybe higher? Who knows.
What I think will happen is that both towers will rise at the same time and there will be a final finish (by SF?
) which will claim dominance.
Notice how all of the press releases during and since the ceremonial groundbreaking claim it as "the tallest building on the west coast?" Pretty brazen. Surely the developers and architects know that the WG is proposed at 1100'.