According the UK videogame retailed ShopTo, a Mortal Kombat compilation is set to release on Playstation 3 sometime in spring 2011. The website lists no details regarding the product, but the timing would make sense considering it would be a neat way to build hype for the next iteration of the series.
Gaming Union will be sure to inform everyone the second we receive more information on this compilation. On a side note, there's a good chance that this title could be going multi-platform as well. Particularly since it doesn't make much sense porting older games to a single console.
Source: Next-Gen News