what will their excuse for not distributing the cash be at that time?
$100 billion is more than enough to innovate. They must release $100 billion back to shareholders by either increasing the divy or offering a one time special divy.
Apple will pile up cash until it has enough to buy back all shares.
and then what? Go private?
Most of AAPL's money is overseas. They can't disburse it to US shareholders.