Hi @thepassenger, I believe we might be seeing anti-aging solutions become available a lot faster to be honest. And I hope we are lucky enough to fall in what scientists call "the longevity escape velocity curve." For instance, scientists Aubrey de Grey believes there is a 50% chance that there are people alive today that will manage to age to a thousand years. You can read an interview with him here.

As for what the earth can handle, I think most people's views on this aren't very optimistic but without good cause. I encourage you to check out the work of Hans and Ola Rosling. The video below is a good place to start. (The presentation starts at about the 6:30 minute mark.)