How old is the Earth?
Yes, the age of the Earth is about 4.5 billion years (4,500 million years). Your linked articles describes well how it was formed and how we know about it. The uncertainty is less than 1% and depends partly on the radiometric dating methods and partly on the definitions. Sometimes the age is said to be 4.567 Ga, that might be a little too exact number to claim, but at least it's easy to remember. 

I haven't heard any different age constraints that are scientifically founded, but before we had access to the methods and data we have today, there was a broader range of estimates. 

Early estimates were based on the supposed increased salinity of the oceans, but those estimates fail to recognize that salt is also removed from the seawater in subduction zones and to form evaporites. 

Noteworthy is Lord Kelvin's very sensible estimate of 20–40 million years, published first in 1863. The estimate was based on the heat lost since formation and Earth's capacity to withhold its energy. Unfortunately, Lord Kelvin worked too early to know that $E=mc^2$, so energy is also generated within Earth and that is the main source of heat. He also didn't understand the Sun's source of energy and convection and therefore miscalculated the solar age constraint and Earth's heat flux. 

Radioactive decay is not only the source of heat but also the process we use to measure the age by radiometric methods. These methods became known decades later and quickly provided age constraints sin the right magnitude. 

Earth scientists have assumed the deep time age of Earth since the antiques. It must have been frustrating for the early geologists to not be able to put a number of the Earth's age. As a rudiment of that time, we still use their relative terminology to describe the development. 

Our present estimate is based on a range of agreeing models and data. The Earth science community has, in general, moved on to new and more challenging questions.