請問如果航班取消, 係咪變左要入下一班機之waiting list? 假如係旺季, 隨後幾班機都full, 係咪要有排等?

In fact it is.  However it may not the case.  You may have higher priority in the waiting list.  The airline depend on your location, reason of flight cancel, etc to determine.  They not want to pay for your free accommodation, free meal etc