I'm not sure if he's going to keep his job or not. The entire outfield is filled with rookies (Scott, Lane, and Taveras). So, I would assume the one struggling the most goes.
I would say they find a spot for Taveras when Berkman returns. But, who knows.
As for "can he keep it up?". Yes. Check out his minor league stats, the man can run! He has ten steals in spring btw. He just has to keep getting on base.