i heard somewhere that Buddhism will ast 500 years, and i heard somewhere else that buddhism will last 5000 years. The first one is obviously wrong, but in the 5000 year one, it says that 500 years after the paranirvana of Buddha, there will be no more enlightened people, or Arahants until Maitreya. which one it true, or do you dissagree with both?
Anyone (even The Buddha) cannot guess how Buddhism will last.
It depends on people.
If There is no one who study and follow Buddhism, Buddhism will disappear.
If there is only one person who study Buddhism, Buddhism can still exist in the world and he can make it propagation.
As you know at first there is nobody, who knew Dhamma.
Only The Buddha knew Dhamma and he made it expanse through the whole Indian subcontinent.
Nowadays some people can study Buddhism easily.
But some need to face so many difficulties to be able to study Buddhism.
Unfortunately the others cannot study it no how.
As a Buddhist I suppose that it depends on individual karma of passed lives.
Some dont have enough karma of good deeds to meet with Buddhism.
I also agree that we (Buddhists) no need to worry about any prophecy. Worry is a kind of impurities of mind. We need to eliminate it by means of meditation.