Well if it was categorized as income, I think the write-off limit is $3000 a year so it will take 10,000 years. If it was a capital loss, he could write it off faster.
I guess he could probably argue it was fraud and not count it as income. Or, if he planned it right from the start it was never income and was instead an investment which he could then write off as a capital loss.
It may depend on how he categorized it. Trump managed to write off his billion dollar loss on his Atlantic casinos, so there may be a way around that.