During an AMC interview with James Gunn, Chris Pratt, and Kevin Feige, when asked if Cosmo would be in the film, producer Kevin Feige said "Fans of Cosmo will have to wait and see the movie." With no denial and the inclusion of Knowhere in the film, I would say that there's a big possibility of Cosmo (the telepathic Russian dog) showing up.
Bad news: Gunn admitted that Bug (a former member of GOTG)was in an early draft of the script, but will not be in the film. However, if the film is successful, there will be a sequel, according to Kevin Feige and James Gunn!