Figuring out the actual time until Chernobyl is safe is pretty difficult as most resources are highly politicized (I wonder why...) and there are certain REALLY hot spots, but considering the high profile nature of it: even when it reaches safe and reasonable levels of radiation, people are going to be afraid of it.
But here is a pretty decent, if not overly scientific, resource to get an idea of things http://chernobylgallery.com/chernobyl-disaster/radiation-lev...
For good chunks of it, it is safe enough for humans. Not great, but if there were a pressing concern, people could live there (keeping away from the remaining problems) comfortably (seriously, you would be amazed at background radiation levels in a lot of residential areas). But there is no pressing reason to, and there are definitely some spots you would want to stay the hell away from.
Fukishima, Three Mile Island, and Hiroshima/Nagasaki are cases where there IS a pressing reason for people to live there, so standards are much lower/more reasonable/whatever.
The surrounding area will be safe long before that but the epicentre will be radioactive for a long time and there is nothing we can really do about it.
- "Fukushima robot stranded after stalling inside reactor" [1]
- "the robot could remain ambulatory in the radiation field for only 50 minutes, and in fact the robot's lower portion was no longer responding to commands" [2]
Poor robots, always being sent in to die alone.
[1] https://www.theguardian.com/environment/2015/apr/13/fukushim...
[2] http://phys.org/news/2005-12-mighty-mouse-robot-frees-stuck....
Today, we don't quite have the ability.
In the future, we will.