The director for Bethesda Game Studios which is currently developing Fallout 4 has announced that players will be able to get romantic in the game.
“We track how [each companion] feels about you. With the humans, it can even lead to romances and that is regardless of whatever gender you are playing.
We spent a lot of time on this mechanic. They have a lot of personality. You can also play without a companion, and we have special perks for if you want to play as kind of a lone wanderer. (Todd Howard)
Should be interesting to see how the romance feature works out in the game and also how important it is to character development in the game.