The photos show Jason Segel and Amy Adams's characters from the first film... but Segel and Adams had previously been announced as not returning for the sequel! Therefore we can assume these are stands-ins and that the The Muppets...Again! will begin where The Muppets left off. The stand-ins are wearing the same costumes from the final scene of The Muppets, so it seems possible.
So far we know that Tina Fey, Rickey Gervais and Ty Burrell are all signed on for the sequel, but don't necessarily think that Segel and Adams are definitely out for small cameos just yet...
The Muppets...Again! is due out March 2014, and is being directed by James Bobin, who directed the first film.