they might be the front runners.
Africa now is the one continent that has not hosted an Olympics (well the one Continent that is liveable). According to Wiki, for 2020, both of these African Cities seem like major contendors for the Olympics and both are in regions that are not high in activities that might be a turn-off for the Olympics (like if Alexandra or Cairo made a bid).
I know that there are several Arabic countries like Qatar and UAE that want to make a bid for the Olympics. Both of those countries are so cash rich that they could easily host it, especially Dubai. In fact Qatar had registered a complaint over the fact that early on they had a higher initial rating by the OOC than Rio but Rio was picked over Qatar. However, Qatar also wanted to host the Summer Olympics later in the fall (perhaps to avoid the extremely hot summer months).
I would love an Olympics in NYC - I could take the train up and attend several events, something I have always wanted to do. However, now that South America has their representation I think it's high time that Africa gets a turn. And unlike South America, there are no good countries to host a Winter Olympic (whereas Chile is vying to get the Winter Olympics in their country and Argentina could host it too).
Here's a good analysis of who is looking to apply for 2020. I also like the idea of India applying for the Olympics - that would be a unique region of the world not yet tapped.
http://en.wikipedia.org/wiki/2020_Summer_Olympics