If it were me, I'd call now and try to get a flight out the next day. Nothing wrong with an extra day in Venice. But if you don't want or can't stay an extra day, how about moving to an airport hotel the night before. There is a Marriott close by with a shuttle service to the airport. I am assuming that the shuttle is privately operated and not affected by the strike. And also assume that the strike doesn't affect the airport/airlines workers. If it does, then definitely rebook now and don't wait.

http://www.marriott.com/hotels/trave...3-75b66089dd79