an enthusiast gamer would not buy (at least i wouldn't) a 1440p capable monitor of just 30". HELL NO! Why? It's simple... on a 30" there is absolutely no difference between 1440p and 1080p (16:9 both btw) concerning graphic quality. I told him before... if he really, really, desperately wants a 1440p... GET AT LEAST 45" and then you'll see a difference...

For movies... same thing... 1080p is at the moment the highest resolution on all video recording. There is no need for a better resolution (for now).

Here's how i see it:
A monitor should have a relative distance between it and the gamer. that distance is directly proportional with the screen size.

Imagine a cinema sized monitor (now that would be awesome and it would have to be at least 2560p). Now imagine that when you play you need to keep all the display in your FOV (even if you can't focus on it all). The less you move your head around... the better (less chances of getting pwned by the sniper in the upper left corner of your screen - get it?).

In any case... it's good to be prepared for the future... but by the time the future gets here... your monitor will be burned out due to over-usage. So better just get a 30", 1080p for now... my personal advice. It's cheaper (a whole lot cheaper) and still future proof (for at least 5 years which is more than the warranty).