Originally Posted by MJ-W4
A point I'd like to add is that a general overhaul of the existing engine takes less time and money and comes with far less bugs than a brand new engine for a new, far more complex system.
A good point MJ-W4, why waste money creating something risky and new when they already have a solid build to base off? A good example is with The Witcher
in which CD Projekt have effectively chosen what can be considered an outdated game engine (the Aurora Engine) but have heavily moddified the engine to create a visually stunning experience that is on par, if not better to the likes of The Elder Scrolls IV: Oblivion. Plus, the Aurora Engine has also proved to be a solid engine when creating games with the uber-awsemness of NWN, NWN II (although this sequel was developed with a modified version of Aurora [and less popular and platform friendly] by Obsidian called the "Electron Engine") and all their fantastic expansions.