The current environment is not the same as what the future environment will be.  New anaerobic environments form as new layer of sediment are deposited, sealing off lower layers from the atmosphere.  If things over the next Billion years remained the same as over the last Billion, you would end up with new pools of fossil fuels.  Sadly, over the next 300M years or so, the Sun will burn up most of the Hydrogen and begin fusing  the Helium that has been formed from fusing Hydrogen and will begin emitting higher levels of radiation, making life on the surface of the earth impossible.  Life will persist in the oceans a while longer, until they boil off, and the atmosphere will be blown off as the Sun goes Red Giant.  This will leave behind a hunk of rock with no trace left we were ever here.

The lifespan of Homo Sap on this planet has always had an end date, all that is happening now is we are probably making it shorter.  Sort of like a smoker shortens his likely lifespan.  You also could be hit by a car, or the planet could get hit by an asteroid.  Eventually everything dies, the most you can get is very old first.  That seems unlikely now.  I give Homo Sap to the Year 2525.

https://www.youtube.com/watch?v=zKQfxi8V5FA

RE