It's all about the new year's spec's versus last year's. I recently bought a 2016 Giant Trance 2 at a $500 price reduction over the 2017. Rode it for a couple weeks and wanted to start upgrading just because that's the way I am.

My LBS has a 30 day replacement guarantee so I looked over the new 2017 Trance 2 and it had everything I was thinking about adding. 1 x drive train, 34 instead of 32 mm forks, boost hubs, new geometry, wider rims etc. They gave me 5% off the 2017 and it cost me $395 extra which was far less than any single upgrade I wanted to make.

If the new bike is the same bike with the same spec's, which definitely happens, then last year's model makes sense but if this year's model is a marked improvement (which I thought was true in my case) the I'd spring for the new bike but again only if those improvements are what you are looking to improve/upgrade.