You're really over-thinking this. The MBA works fine today. It'll work fine next year, and for many years to come (depending how you treat it). Better spec'd models will come along. No, really, they will. And, if you keep looking backwards, you are going to suffer "buyers' remorse" forever. And forever is a very long time.
We buy these lumps of aluminium and silicon because they do work. They're tools. They keep doing work even when a "better" machine comes along. So, do stuff with it until the day comes that you need more grunt or it dies or you feel like treating yourself to a new toy or whatever floats your boat.
I bought a base MBA quite early for ~1,000. Nine months on it looks as good as new, works as good as new, and does the job I bought it for. It's a far better machine than I expect, tbh, and I use it far more than I intended.
I'll need to replace my late-2013 MBP at some point; but here I am looking at the current models and thinking: It does the job I need it to do. It's not dead, yet. I'm fine with the toys I have.
Buy the tool for the job you need it to do. Get on with the job. When the tool no longer does the job you need it to (or you feel like treating yourself), buy a new tool.