Is there a source for this? I don't remember any language to suggest Java Edition would eventually be replaced when they announced Windows 10 Edition. They've always indicated that they intend to keep maintaining the Java Edition, with parity in the core game. The messaging here has never changed, as far as I'm aware.
If anything, they might have just done the rename simply for standardization over 9 different app stores with different requirements, branding requirements, and length limits before truncation occurs.
Pocket Edition was a stripped down version of the game to support the xperia play, so it was built for optimization from the start. Later it got support for broader Android devices and iOS, while Mojang outsourced console development to 4J studios. Eventually, they decided to beef up Pocket Edition to be mostly feature complete with Java, renamed it Bedrock, and made it the de facto standard for all devices, sunsetting 4J's port.