I think Phil knows that if a device like this is going to be successful then it needs to be announced at E3 with a bang and it needs to be on live TV.
This is the only event Microsoft does that is on live TV.
Then it'd be at next E3 with the Scorpio delayed to holiday 2017.
Phil is a smart guy, he's not going to kill xbox one sales this year. The only way I can see MS announcing Scorpio this E3 for release next year is if it's actually next gen and MS has completely given up on the XB1 and doesn't give two fucks about it any more and willing to cut their losses. But the Slim kinda proves otherwise there.