Well if by old you mean NiCad batteries, then yes. Most current major brands have established a battery form factors that have remained unchanged for years. I'd consider the power tool market fairly stable right now. Battery tech is changing, but most brands now actively make sure everything is backwards compatible if it's not a completely new tool launch.
It is fair to say though that sometimes, some brands fall out of favor and are phased out as bigger companies buy out smaller ones. It's the nature of the beast.