It's all subjective man. I have a PERFECTLY good 1080p monitor right now. I plan to upgrade to a 4K monitor once the prices for a standard quality 4K monitor get into the $350 range. I am running a system with an i5 4570 and GTX 760. I'm trying to decide on if I want to get the 1070, the RX 480, or the 1080.
The 1080 future proofs me. I can play all the games I want now maxed out at 1080p. If I want to get a VR headset later on, it will allow me to run VR with no problems. When I DO get around the upgrading my monitor to a 4K monitor, it will be able to run games at 4K as well.
The 1070 does the same as the 1080 except the 4K gaming won't be as good when that time comes.
The RX 480 will allow me to play all the current games maxed out at 1080p for only $200. Once the 2-yr mark comes around, I will then upgrade to a new monitor AND new, more powerful GPU to take advantage of 4K and all of the latest VR advancements.
In terms of your monitor situation, I would get it and get a GPU that can run games maxed out at 1080p. If you're in the market for a 1080p monitor now, I'm assuming you're not looking to upgrade to anything else soon. In my opinion, 1440 monitors are like Iphone "S" models. It's a temporary bridge between 1080p and 4K. Some people buy them the same way some people by the iphone S models while others wait and just buy the iphone 5 or iphone 6 and just skip the S models. In my case, I have a perfectly good 1080p monitor so why would I just put that on the shelf to get a newer 1440 monitor only to replace that in 1.5 years and get a 4K monitor? Some people do that but I would just rather wait. I think that you'll enjoy the visuals MUCH more going from a 1080p to 4K monitor than from a 1440 to 4K monitor. It's no different from playing games on a lower end GPU with many of the settings turned down and then playing the same game on a new GPU with everything maxed out. It's much more enjoyable to make larger leaps than marginal increases. IMO