so long as some idiot does not nuke our planet, it will happen.
Today (er,yesterday) BBC and others announced water below the surface of Mars. several kilometers big.
How long I do not know, but one thing needs to happen on earth and that is longer average lifespan. perhaps even push it with us having cyborg-like features. say 150 yrs ave, and 200 with stem cell regeneration and a collection a 3D printer part replacements for our bodies?
We need longer just for the education required today. Not just science and tech, we also need to become expert at social and psychological concerns, advanced training in creating harmonious societies and assorted community structures, etc.
I know a University professor that has noticed that her students take serious interest of what will be happening 100 years from now. They all expect to be alive then...so,
it will happen