What do we know? The Lord tells us that the gate is narrow and the road is difficult. He also tells us that with God all things are possible. Scripture makes it quite clear that Hell is not empty, but neither is Heaven. In the Apocalypse, we read of 144,000 from Israel and an unnumbered crowd of every nation gathered around the the Throne. Some will be saved and some will be damned. That is all we know.
We should worry less about how many are saved or damned. The Lord Himself refuses to answer the how many question. Instead, we should worry about getting to Heaven and helping others to get there too.