Engine blocks will almost certainly remain as a cast part, simply due to the production capacity of casting is orders of magnitude higher than additive manufacturing, as well as being relatively cheap. Metal additive manufacturing is currently used in aerospace to reduce complex assemblies of parts into a single piece, or to make small complex shapes that can't be made by a traditional machining or casting process. Additive manufacturing, for the foreseeable future will not replace load bearing parts as well, mainly due to the different processing steps load bearing parts undergo. It will also most likely stay with aerospace for the time being, since the price per part is prohibitive for automotive use currently.

http://www.computerworld.com/article/3188899/3d-printing/boe...

http://www.additivemanufacturing.media/articles/the-aircraft...