I doubt it will worldwide, since Deadpool didn't make it past China's censor committee (and Apocalypse will likely do $125-150M there), but Deadpool has a more than decent shot at beating X-Men Apocalypse domestic.
Deadpool's direct competition is Gods of Egypt and London has fallen over the next 3 weekends. Apocalypse has Through the Looking Glass opening on the same day, and then TMNT 2, The Conjuring 2, Now you See Me 2, Warcraft, The Rock+Kevin Hart, and Finding Dory in the following 3 weekends. Not all of those movies will blow up, but they will tie up a lot of screens and have varying levels of audience overlap.