If you're talking about games which require mediocre CPU power, such as BF4 (or BF1), CoD's and other first person shooters/race games, then your CPU will be just fine, both in 1080p and 1440p.
However, if we're talking about (MMO)RPG's, your CPU will be a small bottleneck on 1080p, as those GPU's won't really be stressed out.
But you won't notice a bottleneck on 1440p as it will balance things out.
There's a video on youtube I saw recently showing some top games being benchmarked with a GTX 1080 on 1080p just for the fun and this video might help you further:
https://www.youtube.com/watch?v=7cDMLQosbjw