Should I get the 4S?

I've been waiting for this to happen for a while now. My local carrier just dropped the iPhone 4 as the cheapest iOS option and added the 5S and 5C. Before this they didn't have the 4S, but now they've picked it up as their lowest-priced iPhone option.

So I'm a student and I have a pretty tight budget. I also like to avoid spending excess money where I can avoid it. The 4S will cost me $300 off-contract on Koodo. It's the 8GB model, which I would be okay with. I'd just stuff 4GBs of Music (or 2GBs transcoded to a lower bit-rate) and some apps.

I'm just not 100% sure the iPhone 4S is still relevant. How many people can see themselves reliably using this phone for the next two years? Is it moderately future-proof?

My only other option at this point is the Nexus 4 (16GB) at $150 on the same carrier.