I went thru the same thing just a few mon ago and I pulled the trigger on the '15.

I don't see a lot of major changes down the road in the near term:

Ford developed and built the 6.7 and its a good if not great engine, don't look for them to abandon

HP/Torqe: I see little in that, its at 860 T from 800 T. To go much beyond where they are at requires a LOT of engineering in the driveline. Not sure what the engine can handle but suspect it still has a lot of room left which means driveline mods and they are costly. As Ford left the engine alone until '15 look for this driveline package to continue for some time.

If I am even close to being on target, what is left on the table? Styling, reshuffle the lineup. There are far too many versions of the SD: XLT, Lariat, Lariat Ult, KR, Plt and maybe some others I am not familiar with. Its ONLY options from cloth to leather. Look for more included options at the lower end and more lux at the top end, and maybe a few less versions.

When the dust settled I saw no reason not to go with a '15. I do not think there will be a major change in style (bodywork. Its a truck and when you get past the 250 its because you have a big need to fill. I want my truck to look like a truck, but most of all I want it to perform.

My guess is and its what I based my decision on is that my '15 will be as good as a '16 or a '17, it may look different, but not radically so.

One thing I noticed in my '15, it drives like a different truck compared to my '11, even my wife noticed it the first time she drove it...you are getting a peek into the '16.

Go for it!

 

There is a possibility of lots more than just styling in 2017. Personally I could never live with myself buying a new vehicle a model year before a major redesign. There are always things when the new model info is released that make me feel so glad I waited. I've never once bought a vehicle the first year after a redesign and wished I had the dated version from the year before. YMMV.

 

I just ordered a 15 F350 SRW Platinum. My thinking is when the 17's come out there will be little to no rebates. Also going to aluminum they will probably take a 5-7k price increase on the higher end models, just like the F150's. Your 15 will hold it's value compared to the price increase on the new ones.

I also don't normally purchase 1st year on new models. Buy a 15 now then upgrade in 18 when you will start seeing some incentives.