Of course the speculations are running hot. Two locations? NYC and Hawaii? Off road vehicles! Cars will need gas and car washes! Dynamic time and weather! Many more enhancements to the original game are being leaked. But not confirmed.
those pictures were floating around right at the start of this year and nothing has been heard since, i personally dont think they'll make another one because it would have to be completely different to the first one in a different location otherwise it would just end up being like an addon for the first one.
This is awesome news! Here's the article about it, if someone wants to read it:
http://www.atari.com/news/167