Its possible. Those who imitate others like playing a video game while acting out roles that SEEM stereotypical CAN lead to one being more stereotypical which CAN lead to prejudice and then leads to racism.
However the keyword is CAN. Also the study needs to be a case study or longitudinal time studie to see if they still have negative stereotypes after exposure to the game. It's like saying you just watch an Asian guy drive horribly and the test ask you a question related to your opinion about Asian driver immediately afterwards. Obviously you will think of the driving incident first which will cause a retroactive image of Asian drivers.
Most psychological lab experiments I'm acquainted with have very small long-term effects, as in they vanish after a week. Odds are that they dissipate quicker, but I usually see some experiments do a post-survey a week later. I imagine the long terms effects are the same in this experiment.
That's good news. This concern that video game can encourage racism is probably supported by another concern - that some people play video games too much and base reality on the video game world. Luckily, very few people are like that. It's probably the same argument that people have with reality TV shows and movies. The only difference in video games is you seem to have a more immersive experience which make video game a bigger target than the former two.
I think that is the case they would probably make.....that some people play games a whole lot, so the effects might transition to the real world. Interestingly enough, I imagine they could make games lead to less implicit racism by letting people play as blacks who are performing acts that are more community oriented. I don't know what game does this, but they would probably get results.