Well, if I would have to guess I would say around 12 months from now. Maybe 18 or something. But I'm 100% sure it will happen eventually. Saying that it will never happen is indeed unrealistically pessimistic.
G-sync technology is still very young. Currently all the released monitors are overpriced to milk the most possible money out of people who will buy them on release, plus there are not that many competition on market currently since tech is very new and not many companies makes them yet, so these who do are in good position to overprice them. But later in 2014 they will release many more G-sync monitors and there will be many companies that will make G-sync monitors and market will get more saturated. Plus everybody who would want to get them on lunch would have already spend the money and big hype will settle down. So I'm sure in a year or so time prices will drop lower. Then, once the money from rich people will be milked out, they will start to make cheaper and cheaper G-sync monitors with less Ghz, smaller resolutions, etc for budget prices to get some money out of people who can pay less.
This is how market works. Companies need to maximize their earnings. If they release budget versions too soon or lower prices too early then they will lose money. But once the hype goes down and sales settle down prices are lowered, budget versions are made and products goes on sale to squeeze as much money out as possible. So 12 to 18, maybe 24 months maximum for very cheap budget versions to come out.