Because large conventional discoveries typically take years to develop, it is not as if the shortfall will be felt immediately. Even the past several years of paltry discoveries probably won’t lead to supply problems for quite a while.
There are still large stocks of crude oil in storage, and US shale will continue to grow at a blistering pace into 2018. Beyond that, OPEC has quite a bit of surplus capacity sitting on the sidelines. It might not be until the 2020s until the lack of discoveries starts translating into supply issues.