This has been something I've been concerned about as well. If they want to maintain "realism" with resources then regenerating planets is not going to happen. The best bet in my opinion is mining asteroids. I would like to see both "static" asteroids, ones that are large enough to built a base on/in, and regenerating asteroids that may "collapse" after being mined sufficiently only to re-spawn after a time, probably not in exactly the same place, or with the same resources.
I've already mined out all the veins of Iron on my Sanctuary hex, and am getting close with the rest of the T1 ores. I've only mined a few T2 veins, but there are only so many of them and if I tried I could probably mine out an entire Sanctuary Hex in a day or two of all T1 and T2 ores if that is all I concentrate on. The need for resources is huge. It takes almost 1 and a half Veins (Sanctuary veins are usually 4-5k L of ore) of Iron to make 1 large container. I am at the point where I HAVE to leave Sanctuary and I worry about finding a hex elsewhere that has access to a good market and hasn't already had people mining it because of the ability to mine unclaimed hexes. I have some ideas on ways to regenerate on planet, ignoring reality, but that is for it's own thread.