It's not quite that simple. What has happened ( and is happening ) here in Australia is that those who can afford the considerable up-front costs of solar are doing so, and are getting close to not paying for power. In some cases, they are actually making money from exporting back into the grid. This is somewhat due to a stupid government rule that means they get overpaid, but that aside, it's only the wealthy and middle-to-upper class users who can take advantage of it.
Because utilities are trying to maintain profits, it's not as simple as saying "well, they get more power and just resell it" - They are still paying for infrastructure and stuff to the people who have lots of solar, but who don't consume electricity enough to cover the costs of that infrastructure.
So as a result, their biggest customer base becomes low-income earners, who can't afford to pay for solar and who can't afford to carry the infrastructure costs for wealthy people either. The result is that the ability of the power utility to increase charges is suddenly curtailed because the less wealthier customers can no longer afford to support them.
This is known as the "Solar Power Death Spiral" - because the more that the costs go up for the remaining market, the larger the adoption rate of solar and, again, it's the wealthier part of the remaining market that makes the move first.
And yes, it is very real and the utilities are terrified of it... It's not a threat to electricity generation or other things - it's a threat to profits and to the utilities ability to incrementally charge for their costs with a customer base no longer able to pay for it. Sure, greed is a huge factor, perhaps the only real factor, but the utilities will defend their market vigorously. The likely solution is that they will change their charging model, where you end up paying an "infrastructure cost charge" regardless of whether you use power or not, and a usage tariff on top of that. This will redistribute the cost again and make solar uncompetitive. And they will quite likely make "opting out" illegal too... So expect to pay an "infrastructure cost charge" even if you don't have a connection to the grid, so long as it's possible to connect where you are.
That's how they did it in Australia with water, except they also made water tanks illegal in parts of Australia before drought and dwindling infrastructure became such a constant problem.