On his Facebook page, Guardians of the Galaxy director James Gunn made a post about Hollywood suddenly focusing on making shared universes before making good movies. You can read his post at the link above. The interesting thing started happening in the comments when Gunn responded to a few questions.
He was specifically asked about Nova making an appearance in the sequel.
I don't want Nova right now because I think Quill being the only earthling is important. That serves the entire movie going audience and not just the handful of Nova fans… I have nothing against Nova in future movies, but it doesn't serve the movie right this moment.
He also said that the MCU is not quite as planned out as we think it may be:
The ONLY thing in GotG that was connected to the rest of the Marvel Universe is the existence of Thanos and the existence of an infinity stone. Everything else – how Thanos was connected, who he was connected to, what were the properties of the infinity stone, etc, etc, were all basically made up by me. It's much much looser than people think it is. And it certainly wasn't planned out when they did Iron Man. They just thought about making a good Iron Man movie – which is exactly my point.
He also commented about the perceived feud between Marvel and DC fans.
Neither Marvel nor DC is "flawless," come on. And how come you guys love to fight about Marvel and DC is beyond me. We're not rival football teams.
Guardians of the Galaxy 2 will be in theaters May 5th, 2017.