We need better crystal balls...
About a year ago (summer 2017), I planned a trip to/through Turkey for summer 2018. Booked flights, started planning. Then there was a diplomatic kerfuffle between the current US administration and Turkey's (actually there were multiple ups and downs, but one major "down"). In the fall of 2017, Turkey stopped issuing visas to US tourists. That persisted for a month or so. During that time, many of us watched and started to worry about trip plans. I eventually changed my plans around the beginning of December. I was able to cancel my flights and rebook a different trip at no cost (thank you, United Airlines, for doing the right thing). About a week later, a "diplomatic breakthrough" was announced, and visa-on-arrival for US tourists started again.
Of course, lately I've been thinking about that trip to Turkey again, for next year.
Now, recently there's lots more drama between the US administration and Turkey again. And the trend lines are going in the wrong direction. Everyone should make their own decisions, but I'm putting the trip to Turkey on the back burner again (and I just booked next summer's trip to Ireland and the Faroe Islands - I hope Trump doesn't start some snit with them). My guess is that things between the US and Turkey may settle down in the coming months, or may get worse, but will probably not return to something like stability until one or both countries enjoy a change in leadership. What's going on currently is a shame for a multitude of reasons, but for me, I'm going to give it some time before I plan the Turkey trip. It's a shame, I really want to go (and I am not one who easily is spooked by political news) but when they routinely deny entry visas for tourists, it's important to pay attention. YMMV.
If you do plan a Turkey trip, it's worth noting what the policies are about cancellations and rebooking (check with airlines and tour companies). And of course, pay attention to developments which could impact your ability to go.