IF, U2 is going to tour in the first half of 2017, it should be announced soon. Many bands are announcing tours and tickets have or will go on sale soon. (Last leg went on sale 6-11 months before the performances)
I cannot see them playing in the first half of the year, and the longer we wait does not bode well for a tour sooner than later. Sad! I am looking forward to seeing the Red Hot Chili Peppers, Green Day and Roger Waters in the first half of 2017. But, I'd trade those for U2 in a heartbeat.