So it is year 2024 and the max BTC supply is reached at ~21M.
Wrong. We will be there approximately at the year 2140. The bitcoin as block reward or
subsidy halves every 4 years that's way it will take much longer than you think.
Will it be economical to continue mining BTC going forward?
Hard to say but someone should've discovered something that would make the production of electricity cheaper. And also someone should've made something significant in making mining more efficient.
Is it possible that the S/W for BTC may be augmented to a semi POS type of system?
Not sure how to answer this but I doubt this will happen.
Even though the difficulty might increase, isn't it possible that (even with the electricity thing) that the gpus that far in the future will be super powerful? What if they start mining coins without any issues at all?
Does that change anything about how long it'll take to get to 21M or am I completely wrong?
I don't know much about the workings behind mining and I've always wanted to know. I'm sure these are questions that others might have.
They are working in the lighting network so I think they are still has a long way to go (because if they are thinking on another way, they will put thier resources in discovering other alternatives to mine) not build a LT.
Same as you I dont have any knowledge but Im hoping that the Microsoft giants or other big companies will participate on the blockchain and font a way (a greater way to mine this cryptos).
Will it be economical to continue mining BTC going forward? The large mining operations can always set up a solar panel system to reduce energy costs.
Just putting up solar panels means nothing.
If the thing you do, be it mining, manufacturing or anything else is not profitable then it's stupid to build solar panels and use that energy for it. It would be far better to just sell the energy you make with the panels.
Solar panels are only efficient for off-grid systems, because of its high initial price, people will choose the grid. And if someone will build solar PV system, they will profit more on incentives and like you have said, selling electricity than mining BTC is the best choice
We have a lot of problems in the supply of energy nowadays, if this mining will caused so much power then this will not be efficient in the long run, what i mean is it is better to give people the power sources than spending it on mining IF ONLY they cant find a way to mine in an efficient manner.