The Super Bowl runners-up are one of four teams due to play at Wembley Stadium this year, as they face the Jacksonville Jaguars in October.
York told Sky Sports News: "Clearly the number of [London] fans has grown. The media attention has grown and we've had no trouble selling out the tickets.
"This will be games number seven and eight and this will be the first time we will be playing two games [at Wembley] and all sold out. We've taken real steps with having the two games and I think that we will progress beyond that.
"I don't know there is any set timetable and there are complex issues with the logistics of travel, but we're trying to take care of those things as they come along and not go too fast, but I believe the potential is there to have a franchise in London."
The Minnesota Vikings and Pittsburgh Steelers will also play in London in September.