I suggest saving up a bit and going up another level in video card speed if you want a laptop for gaming for 3 years. Or be OK with running on low settings in newer games, with possibly lower resolutions as well.
i think you cannot go higher than 960M within the price bracket. Easily last 3 yrs? hard to say considering it's not very high on Maxwell based mobile GPU hierarchy and there's already Pascal stuff out, full desktop version no less. If you haven't already, check out the detailed review here: http/www.notebookcheck.net/NVIDIA-GeForce-GTX-960M.138006.0.html
Seems it's able to run modern titles on med at 1080p or in some cases a lower res. and achieve playable framerates. So, you can take that into consideration when trying to figure out how it should fare a few yrs from now. i'd estimate you could be able to run future titles by tinkering with the graphics settings and making compromises on visual quality/resolution.