Has Disney officially put out a statement saying that it'll start on Monday? Not that I'm aware of. Though there were reports that Disney told travel agents that FP+ was coming for off-site Guests "in the near future".
But knowing the connections that Steve and this site have, if he posted it as an official news item like he did today, he's extremely confident that it will actually happen. (It's also been proven many times for many different subjects that this site often knows about things happening in WDW well before 90% of the cast knows it...)
-Rob
Good to know..thanks for the info! Guess I'll hopefully wait for Monday