We already know that its made by SG.
Already in December 2013 the Gaming Mag "OnlySP" reported, that SG will work on a MW4 for 2014.
It plays in Asia/Europe in 2018.
It continues where MW3 ended.
Many old characters will return.
All the Infos ( and more specific ones ) are in the Link below.
We have to see, how legit this is.
CoD gets leaked from time to time, so this wouldnt be a surprise.