If Mafia 2 proves to be a successful product for 2K Czech, there will likely be a third entry in the ongoing series: Mafia 3.
As there was a seven to eight year gap between Mafia 1 (published in 2002) and Mafia 2 (published in 2010), it is likely that Mafia 3 would be published circa 2015 or 2016.
In terms of era, Mafia 1 was in the 1920s/1930s and Mafia 2 is in the 1940s/1950s. Perhaps Mafia 3 would be set during the 1970s/1980s? Would the setting be Miami or Las Vegas?
I imagine 2K Czech might draw inspiration from The Godfather 2 and Casino; thus, if Mafia 3 is ever made, it would be set in Las Vegas during the 1970s.