They might be distributing their holdings to most of the exchanges,circulate and cashout it little by little so the IRS wont notice any of their moves,they are safe to taxes which if they were caught would give us dooms,the exchange would surely be closed by the government for tax evasion.
i think cashing out thru exchanges is very likely option, however it is how you move funds from exchange to the banking system. You would have to explain source of fund and source of wealth, once bank gets wind of funds originating from ICO, red flags!!! and most likely the account will be closed off.