Similar announcement re the lavs was made right before boarding my PHL-LAX flight a few months ago, and everyone sort of freaked out (myself included) and ran to the bathrooms.... only to find out upon boarding that what the gate agents should have said was that the lavs would not work UNTIL after takeoff and we had reached a certain cruising altitude.
Interesting. Our onboard crew said that people should be able to use the bathrooms once we were in the air, but would have to use bottled water to make them flush. No idea how that's supposed to work; I didn't use them myself.
PHL to LAX is a heck of a long run without working water. At least this morning's flight was only a couple of hours.