I wouldn't write Perez off, because he is still young, but I don't see him as a starter in Washington. He has absolutely no power. He's got to get on base to make a difference. He really needs to get more selective at the plate and take more pitches to become a big league starter.
I guess you can make the argument that our offense should be really good(if Morse, Zim, Rendon, and Harper are all here and playing to their capabilities) that we an afford a defensive minded CF, but I don't think we'll need to concede something in such a big way.
I think Werth/Harper man the CF position for the next couple years, until Goodwin or Michael Taylor can take the position. Taylor's got to get on base at a higher clip as well, but he at least brings some pop, but also did considerably better in the second half than the first(.266obp in the first half, .351 second).