Kind of depends on your carrier plan and how flexible it is. I'm on T-mobile with the JOD program so I can get 3 phones within one year. I turned in my Note 7 for the S7 Edge, I'll jump to an S8 Edge when it comes out and hang onto that to see if there is a Note variant that comes out, if one does get released then I'll use another jump to get that. I prefer the Note line so in the past I have only upgraded once a year. If your plan doesn't allow you to be that flexible then I'd wait for the S8.
In regards to the pre-order, I did it for the Note 7 and I'll do it again. Hopefully this was a one off instance, yes it was annoying to deal with it but at the same time I got two 256GB cards and a VR out of it with all the promos and having to swap phones. My loaner was an S7 and the rep told me to take advantage of the VR promo, I explained it was just a loaner while I waited for the replacement Note 7 and he said it didn't matter and that I qualified for it. So all in all I got about $500 worth of promo stuff.