I'm not sure if this is intended or if it's a bug:

After updating Minecraft to 1.8, I got a little bored on my Survival world decided to go find NPC Villages to trade. Call me lazy, but I used a map viewer tool (it's not a mod, it doesnt change game files or java stuff) called AMIDST 3.7 to find villages, strongholds, biomes, etc. As far as I know, this tool only views the save files not alter it or corrupt it. So I followed the map on a little quest to go to the NPC Village it located and it showed that a near village is by the end of the river near the edge of a jungle. so i followed the river but once i got 10 blocks or so away from the coordinates of the supposed NPC village, nothing was there. The biome that AMIDST shown is that the village is on a River/Plains biome. Instead (btw i was using 1.8 to explore in the game) it was on a savanna.It was weird because I know i created my Survival world on Minecraft version 1.5.1 release and savannas biome didnt exist at that time. It was also weird that the game seemed to completely regenerate a part of the world(probably because of 1.8) beyond a certain exact boundary (which happened to be at the end of my Quest). Thats's what i believed what happened, the version was updated and part of my world got completely regenrated. So the question is: Is it normal for the game to regenerate part of my world when i update the minecraft version? it's as if theres a fine line between my regular world and the regenerated world

I also noticed that whenever there's a version release like 1.6, 1.7, or 1.8 and it comes with new mobs, ores, etc, my survival world doesnt seem to apply them. But beyond this regenerated boundary (which i talked about above), the world seems to be applied 1.6, 1.7,or 1.8 stuff like horses, rabbits, diorite. It was good though that the game allows objects to pass through this. I got a horse through the boundary without any glitches and hooked it on a fence with a lead. I was glad I discovered that regenrated part, so i can bring in recent additions like new ores, mobs, etc.

I apologize if the whole issue sounds unclear, just reply if you need clarification. Thank you.