Great article. I've used this philosophy recently on a fantasy hockey keeper team (winning now) and a fantasy baseball keeper team (winning in the future). It's a sound strategy as long as you know what your team's focus is.
On the fantasy baseball team, players can be signed on your team for a maximum of three years once they reach the majors. So although I am dumping for the future this season, I have a two-year window after this one where I can keep my team built around three core up-and-coming players on inexpensive salaries - Carlos Correa, Francisco Lindor, and Miguel Sano.
The challenge here is sometimes it's hard to predict when that veteran will start falling off the map. With Martin St. Louis, it seemed to happen fairly quickly after some great seasons beyond age 35. With other players (eg. Chris Chelios), this can seem like it goes on forever.
Back to the fantasy hockey team: I was in contention last season and managed to trade Evander Kane this way. I also nearly traded Olli Maatta. Both players were out for the season by the time I made my trade offers, but the other owner would get to use them next season. The rentals I received in return (Keith Yandle, Steve Mason) on the final year of their contracts helped me win another championship, even though Kane may very well have a great season in Buffalo in 2015-16.