There’s a lot more nuance to this than most people will admit.

Net metering is 100% unsustainable, when renewables become a big enough chunk of the grid generation mix, they often generate when no one needs the power. Forcing the grid to accept that power and even pay the homeowner a premium for it is a perverse incentive. Effectively what it does is allow solar array owners to avoid paying to maintain a grid they still use, and since the rich trend to go solar first, the poor are left holding the bag to maintain the grid for everyone.

Just pointing out that the grid is paid for by your electric bill, roughly half of what you pay is for delivery (paying to maintain the equipment needed to deliver you that energy), the other half is for supply (paying the power plant that generated the energy). So even if you and all your neighbors are energy independent you’ll still be on the hook for at least half your bill, or they’ll have to recoup it in taxes or something.

Not saying that’s a bad thing, just clarifying a common misconception that going solar should not mean you eliminate your electric bill. In fact many places where solar does offset 100% of your electric bill are ending up with the rich owning solar and the poor paying to maintain the grid for them.

Yes and no, the progress of solar array technology continues unabated, with multiple areas of research that are beginning to reach commercial applications. Module conversion efficiencies now are in the 20% range, but heterojunction cells, or Gallium Arsenide, or Perovskites, or any number of other possible advancements could easily put efficiencies up into the 30% range.

That being said, the price of the solar modules themselves has already shunk to a small piece of the cost to build a solar array, with the bulk of the costs now being the support structures, wiring, electrical equipment, labor, development, etc. And those costs aren’t going to decline, they’d still be there even if the solar panels themselves were free, so they effectively set a floor to the cost reductions we’re seeing.

Could it be worse than giving them to power hungry octogenarians?