The Grand Prix of America will not be taking place next year due to various things, and will now take place in 2014. I'm quite disappointed, as it looked like it was going to be a good race. Now there's the question of what race could theoretically replace it. I've got a couple of ideas.
Turkey
Ever since I went to Turkey almost exactly ten years ago, I wanted a Turkish Grand Prix, and when it was announced that it was going to happen, it felt like a dream come true to an extent. I was disappointed when it was removed from the calendar this year, and would gladly see it return.
France
There have been talks for a while about France returning to the calendar at either Magny-Cours or Paul Ricard. This could be popular, but funding may be an issue, plus the teams know Paul Ricard like the backs of their hands, so the race could be boring.
Imola
Imola. A good track, and very popular with the fans, so to see it return would be wonderful for many people, myself included. I've considered the possibility of it returning ever since it was dropped several years ago, and with the removal of the final chicane and a new pit complex, now may well be the ideal time.
London
Bernie's pet project. It could take a lot of work, but it'd be popular with fans and broadcasters, and quite possibly the teams, too.
Of course, there may well not be another race next year - we could be left with 19 - but there's still the possibility of a 20th race happening.
EDIT: Bernie has apparently confirmed that it is unlikely a replacement race will happen.