If you create a new project and you have the latest GCC, then it is no trouble for you to add the -std=c++14 into your build config and write C++14 conformant code.
However, if you have dozens of legacy projects that all have to be recompiled regularly (say, for each Ubuntu release), then you have more than enough to worry and duct-tape even without compiler suddenly changing its default behaviour.
One more consideration. To whom do you plan to distribute? Only to platform, where you develop? Or perhaps to as many platforms as possible? Do they all have a C++14-supporting compiler? Do you use third-party libraries? Do they work with C++14?