Jonas Brothers at their peak had an album start at over 500k. It's totally possible. Esp since only Nick compares to Louis, Harry, and Liam. Joe is at Zayn's level. And even Niall is better than Kevin.
As for Taylor: even if she gets only a 750k opening she'd be the first female to have hit that mark twice (Britney had 746k.). And the 2nd female with 3 weeks selling 592k, after Britney.
Are their predictions based on released singles? Carly Rae Jepsen and Justin Bieber's (well ) predicted numbers were way higher than their actual opening sales. I would not underestimate the Lord, though.
If both Taylor and One Direction reached those #s it would oviously be huge for both, but I don't wanna get my hopes up based on early predictions. I do hope Taylor sells another million though, and One Direction selling above 500k would be