Chinese American
Hamtastic Knight
The game would run like pure crap.
LuaJIT is very fast and almost approaches C/C++ in speed. There's also Havok Script, which is basically Lua with (proprietary) optimizations and enhancements, and is used in many AAA games across all the major platforms and consoles. Just found out that Civ:BE already uses Havok Script. So the transition should be seamless to develop the new game in the series almost entirely using the same, fast, powerful scripting language.
There will be many benefits. This will simplify development for the developers. They don't have to go back and forth between C++ and Lua. Changes can be tested almost instantly without recompile and restart application. New concepts and content can be created and tested more rapidly. i.e. new DLCs, civs, traits, etc.