So this opens the door to newer technology, etc, coming out that changes these estimates yet again.
"So this opens the door to newer technology, etc, coming out that changes these estimates yet again."
Yes, but you have to understand something about these techniques, and how they interacted with hypotheses about the Earth's age.
The old estimate for the age of the Earth was what is politely known as a "SWAG" (Scientific Wild-A$$-Guess). Essentially, the natural philosophers who assembled the geologic column (all of whom were creationists, BTW) estimated how long it would take for certain features to form, based on an assumption that the continents pretty much came into being in their present-day positions.
There was a maverick named Wegener who looked at a map of Africa and South America, and concluded that the two continents fit together neatly. He hypothesized that the continents were actually in motion. Well, his hypothesis had some serious flaws. The most serious flaw was a byproduct of the flawed assessment of the Earth's age, which dictated an extremely rapid rate of movement--something that would be detected even by the relatively primitive geodetic instruments of his day.
In the 1940s and 1950s, new technologies appeared that revolutionized our understanding of geophysics. Three are particularly important. The first was sonar. This showed us undersea features that we had no idea even existed prior to using sonar for depth-finding and the like. The second was radioisotope dating, which showed us that the Earth was many times older than we thought. The third was the magentometer, which allowed us to view the magnetic alignment of the seafloor.
When all these were taken together, Wegener's hypothesis of continental drift suddenly looked a LOT more tenable. The results from all of the observations made possible by the new technologies pointed to a much older Earth--and they pointed consistently across multiple disciplines (geology, chemistry, physics, biology, botany, and so on) to an age of about 4-5 gigayears.
For a new technology to revise the age of the Earth drastically in one direction or another, there are two things that must happen:
1. The new technology must actually show an age well outside the 4-5 gigayear range;
and
2. There must be a hypothesis to explain why the other ranges given to date are so far off from the new technology's estimate; in order to become a theory, the hypothesis must make predictions that can be successfully tested against observation.