(Gallium is a byproduct of aluminum production. We aren't going to run out.)
Unless by “make from something” else you mean extract the element from existing chemical compounds found in Earth, in which case we’re still just using existing deposits on Earth.
The earth's crust is 8% aluminum.
We will have bigger problems before hitting this one.
We will not remain without gallium, but it is impossible to scale up the gallium production to a higher level than provided by the current productions of aluminum and zinc.
So there is a maximum level of gallium that can be used per year and it would not be possible to increase the production of blue and white LEDs and of power transistors above that level.
Fortunately, the amount of gallium used per device is very small, so it is not likely that we will hit that level soon. A much more serious problem is the associated consumption of indium, for which the resources are much less.
The metal isn't going to disappear, but it won't be concentrated enough to be as easily retrievable.
I'm inclined to think we've lost that gold.
In your question you stated the running out as a given fact ("When" we run out, not "if").
If that was what you wanted to say I can't tell you, but that's definitely how it was received and thus you also got the harsh response. Since it reads a lot like doomsday thinking.
(Example: Does that mean when we run out of oxygen there are no more humans?
Why would we run out?)
You still seem to be missing the point.
If you talk about "when we run out", you are presenting yourself as an expert stating "we will run out" and asking about the aftermath.
It would be appropriate, and better received with more leniency, for you to ask whether we would run out.
Of oxygen, because of rising temperatures interacting with rock weathering binding all the oxygen.
Now, that's more of something to worry about at geological time scales, but Earth in fact, is not infinite.