Yes Hot Peppers or Jalapeno Peppers do become hotter and hotter as they ripen.
So the longer you allow the Jalapeno Peppers to ripen the hotter the pepper will become.
When Jalapeno Peppers are green they're hot but not as hot as they would or will be once they turn red and become riper.
So if you want your Jalapeno Peppers to become hot and I mean really hot you should allow them to fully ripen first before eating them.
The longer you let the Jalapeno Peppers ripen the hotter peppers you'll have.