The loss of ability to use my AA LT Plat status to get free access to exit row seats on Alaska. (I don't care about the earning, since I don't fly enough to earn any status through flying, so I choose to earn AS miles on AS flights and AA miles on AA flights.)

As a tall-ish person, it'll mean I have to factor in the cost of the extra-legroom seats on Alaska flights, and thus my cost for flying Alaska will go up a bit, so I'll consider other airlines more on routes up and down the west coast, since AS won't have the price advantage of "no extras to pay for" anymore for me.

And the growing use of Basic Economy fares, without an easy way on most OTAs to filter out all Basic Economy fares, is making price comparison between airlines trickier.

The biggest changes likely to affect me that might come in 2018 (but haven't been announced yet) are due the merger of Marriott and Starwood, including what happens to the United Silver I'm getting from Marriott Plat and the Delta quasi-status that I'm getting from SPG Plat (which in turn I get from being Marriott Plat). But it's not yet clear if those changes will take place anytime in 2018, or if only the announcement of them will come in 2018 but implementation in 2019..