For the third year running, we're getting a space blockbuster in the fall. Ridley Scott is obviously a renowned sci-fi director, and as the biggest science fiction movie of the year, fans of the genre will be turning up to see how this turns out. As the movie's advertising has grounded it to earth, showcasing an American theme of 'leave no man behind', it will appeal to a very wide audience. Comparisons to Interstellar and Gravity are inevitable, but the trailer for the movie has been more widely seen than both of those.
This is Fox's biggest tentpole release in 2015, and as such they will be giving it as much promotion as possible. Awareness is high already (at least where I am) and anticipation will grow in the next two months leading up to release. It will be the biggest film in several months, so it will receive strong press coverage and mainstream audiences will have a reason to go to the cinema again. Opening weekend it is facing very little competition, and if all goes in its favor - including potentially very strong reviews - then I think this can outgross GRAVITY in its first three days.
Maybe it sounds like too much, but there's a demand for big-budget space movies and it will be satisfied. Who's with me...