The National Football League has played eleven games in the United Kingdom since 2007, with all of those games taking place at Wembley Stadium in London. While Wembley will continue to host NFL games, a second venue in the UK has opened their doors to allow the NFL to play games at their site as well.
Tottenham Hotspur, one of the clubs from the English Premiere League, has reached a deal with the National Football League that guarantees that at least two games per year will take place in their new stadium, which is set to open in the summer of 2018. That agreement stretches for ten years, so there will be games taking place at the currently unnamed venue through the 2028 season.
The agreement also does not preclude NFL games from being played anywhere else in the United Kingdom, so the league would likely continue to use Wembley Stadium for games as well. It has not been clarified, however, how many games per year the league intends to have at international venues going forward.
The NFL International Series started in 2007, and one game per year was played in London from 2007 to 2012. The league expanded that to two games in 2013 (one of which featured the Minnesota Vikings defeating the Pittsburgh Steelers), and three in 2014. The league will play three games at Wembley this season as well.
With the new stadium coming online at around this time next year, it's pretty unlikely that the Vikings would serve as the "host" team for a game in London any time soon. But there appear to be more opportunities opening up for them to serve as the visiting team in such a contest.