They will either announce prior to the open or placea Trading Halt first thing Monday.
If it was up to me I would place the company into a Trading Halt prior to the open in the morning and then let the market stew for 2-3 hours after the open so it has everyones undivided attention and then wham watch it take off prior to the close for the day.
This is what I would do. (not illegal, not immoral)