Given that an increasing percentage of NFL revenue comes from the International market, it is is inevitable that there will be teams outside the US in the near future.
The Jags interest in moving to London is well known - their owner is based there and owns a soccer team. The logistics work better with 2 teams in Europe. I'm surprised that the Chargers are being named as a possible London team - it may be a mistaken assumption by journalists. Maybe they are the other European team.
Some random thoughts:
1. The mainland European team will have a much bigger market. As successful as London is, the football market in Germany is multiples bigger.
2. London games are more than twice over subscribed for tickets, so 6-8 games will sell out. A London team will likely play c.2 games per year at other UK or west European venues.
3. I dont think the NFL will move a team to London until the Brexit crisis is resolved. UK is too uncertain from a ecomonic and civil order perspective going forward.
4. I believe the NFL has looked at strategic training bases in Europe with a view to having a permanent training facility - outside UK, but convenient to UK and Western Europe that all travelling teams can use for their few days in Europe. (Hint - there is a country in Europe that has US customs and immigration officials based in its airports which makes everything easier from that perspective. As a consequence, this country is the only European country that can take flights in/out of local airports in the US which helps with team charters.)