James Hibberd at EW.com is reporting that HBO and GoT's showrunners are both aiming on seven total seasons for Game of Thrones.

Following up on the Vanity Fair article about GoT in which George R.R. Martin admitted that the show might go into unwritten A Song of Ice and Fire territory sooner than expected, EW.com's reporting makes that eventuality happen even sooner.

To quote David Benioff,
It was our unstated goal, because to start on a show and say your goal is seven seasons is the height of lunacy. Once we got to the point where we felt like we're going to be able to tell this tale to its conclusion, that became [an even clearer] goal. Seven gods, seven kingdoms, seven seasons. It feels right to us.

The Vanity Fair article and the EW.com reporting both make sure to mention that eight seasons may occur instead of seven, but seven seems to be the more affordable and realistic number. If true, then the future of the show and books looks something like this:

HBO Tentative Schedule for Seven Seasons
2014: Season 4 finishes adapting A Storm of Swords, starts adapting A Feast for Crows and A Dance with Dragons. Season 5 films.
2015: Season 5 finishes adapting A Feast for Crows and A Dance with Dragons, likely to start adapting The Winds of Winter. Season 6 films.
2016: Season 6 finishes adapting The Winds of Winter, starts adapting A Dream of Spring. Season 7 films.
2017: Season 7 finishes adapting A Dream of Spring.

GRRM Tentative "Best Case" Schedule
2014: GRRM continues writing The Winds of Winter.
2015: GRRM publishes The Winds of Winter, starts writing A Dream of Spring.
2016: GRRM continues writing A Dream of Spring.
2017: GRRM publishes A Dream of Spring.

Best of luck to everyone involved in making these two universes work well with one another.