However, eventually (hypothetically speaking) we will ran out of important resources, which are necessities for our maintenance and survival on planet Earth. Just for an example, the continuous extraction and contamination of water, will ultimately lead to minimal healthy, fresh water supplies and access, therefor contaminating the agricultural industries, causing a shortage of food supplies, ultimately resulting in starvation, desperation, poverty and loss in many human lives.
Alternative energy sources will not be able to 'save' or maintain us as a whole, whilst the continuous growth in the worlds population is still currently in place. Especially those within in, the less fortunate third world countries, whom are susceptible to experience the worst of all of this ^.
As you can see one things leads to another, the ripple affect, as it's commonly known as, though this is all hypothetical, of course. We can predict what will happen in the next 100 years or so, however we can not know for certain what will happen.