I'm surprised that they've opted for someone so much younger than Tom. But, even more so, I'm surprised that they've opted for someone so much TALLER than Tom! There's a good 10 inches between the two - 5'7" versus 6'5". The poster is going to look like Arnie and Danny DeVito in Twins!
Chris Hemsworth towers over Robert Downey Jr. (who's the same height as Cruise) but it wasn't an issue in The Avengers.