Should I wait for other phones?

I have a iPhone 5, I want the LG G2 but I hear the S5 will come out in a couple of months. I want to sell my iPhone now cause I don't want its resale value to go down. I don't know if I should stay with iPhone and wait for a better phone to come out or sell the iphone now pay $50 or so to upgrade to the LG G2 and then do the same for the next phone to come out. What do you think I should do?