The i5 will probably be fine for a few more years, as long as you're not doing really hefty stuff. My recommendation: the more RAM you have, the more future-proof it will be. 8GB is the average these days, I'd say. I upgraded to 16GB this past summer because I desperately needed it for what I was doing (audio editing/mixing/mastering, video editing, image editing, gaming, etc. The good thing is, RAM is super easy to install so you could always upgrade later when needed, but you should start with 8GB as a minimum these days.