If so why/why not?
Things to take into account:
Trump mentioned 9/11 as one of the motives for the ban- however the main nationalitesof the hi jackers (Saudi Arabia, Egypt) will not be effected.
Islamic terrorism in the US is very low. That said maybe that's because Islam is not the size it is there comparable to European countries.
By far the bigger problem is Domestic home grown terrorism (e.g. the over 300 uk born people who joined Isis) - however arguably cutting off their supply of potential new recruits could help.
Trump says current US policy discriminates against christians- figures show the ratio to be roughly equally balanced ( just over 3800 muslims and just over 3700 christians)