If you want to play it that way... he's still be in the top 20, it won't/doesn't change anything, official's just a word here, it really doesn't mean anything, the ATP are doing the exactly the same thing right now.
It won't, but it hasn't happened yet. Slasher's rankings and the other site are just projections, predicting what the ATP will do. It causes celebration, and rightly so, but it isn't official until the ATP says so. Its like the USA's elections, where the results of the states are projected, and the candidates 'win' and celebrate on those projections, but it isn't official until the Electoral College announces those results.