GM decided to tease the upcoming 2014 Chevrolet Impala full-size sedan and the 2013 Chevrolet Traverse family-friendly crossover ahead of their world debut at the 2012 New York Auto Show.
Chris Perry, vice president of Global Chevrolet Marketing stated that "The momentum at Chevrolet continues to build with the debut of the 10th
generation of the Impala, one of the brand’s most enduring and cherished
nameplates," "The new Impala further strengthens Chevrolet’s passenger car lineup by
giving consumers a full-size sedan that balances the desire for
distinction with engaging driving dynamics." 
The teasers show the Impala’s C-pillar and a section of the Traverse’s center console, so we still have to wait until April apparently, before we can offer any substantial details regarding these two new models.
The Impala nameplate debuted in 1958 and has always been one of Chevrolet’s best selling models. 
As for the 2013 Chevrolet Traverse, GM claims that it will come with new styling elements inside and out, as well as with new industry-exclusive safety features (a front centre air bag designed to protect front passengers in far-side impact crashes). 
Perry said that "The new Traverse builds on the success of the current model offering a
wide variety of improvements to ride and handling, interior materials
and exterior styling without compromising the functionality and
capability families need to support their busy lives".

Source: GM