There no logic in hoping that new people keep coming. With a high turnover rate will only allow for a lot of bad reviews which will turn away new people from even coming into the game.
But since it's free, people may be more willing to try playing regardless of the reviews. On the whole, reviews mean less to a consumer if you don't have to pay to try it for yourself. The biggest reason people read/listen to reviews is "is this game or product worth the money". A F2P title costs no money, so the reviews hold little merit. Now if a string of professional reviews start claiming that STO F2P is so bad it's not even worth your time (which truthfully is not out of the realm of possibility), you may have a point.
Also, people can stop playing and still give a positive review. If you play for a couple months, exhaust what content there was but enjoyed it, you could easily stop playing, yet not leave the game with a negative opinion (aside from perhaps that there was too little content).
But by looking at the changes Cryptic has made for the F2P model, it's abundantly clear that they're targeting the high turnover, casual MMO gamer market, perhaps hoping to con a few dollars out of trek fans who would pay to have a more "trek-like" experience with canon ships and uniforms.