If there is a fork, than XT has already won.
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That would be the case of reaching complete consensus with the economic majority. AFAIK 75% (needed by XT) will cause a noticeable split, and thus this can be achieved.
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There will be a period of time in which this will be possible to do. If you think that everyone will switch (all miners and merchants) the first day after the fork, then think again.