According to BP* at current product levels the world will RUN OUT OF OIL in 53 years. What happens then?

Yes - I have heard that estimate too, along with a figure of about 100 years for coal.

It does assume present rates of finds, extraction and use; but whilst there probably reserves yet to be found, it will run out eventually.

So you question is a very important one, and I fear it is one that most politicians and campaigners either fail to see, or ignore, because they are so obsessed with ending the use of "fossil fuels".

Essentially, no more of those products can be made unless satisfactory alternative materials can be found. Salvageable materials can be eked out for some while yet but these too will slowly disappear by simple loss, permanence of items and deterioration.

One alarming point is that all the  things we are told we will all need, such as all-electric homes and transport, rely so very heavily on materials made from petroleum derivatives that using them in solving one environmental danger will only hasten other dangers even harder to solve!