https://www.comicbookmovie.com/thor...e-some-major-new-additions-to-the-mcu-a151390
Found this to be a very interesting find. With the new Guardians of the Galaxy ride at Disneyland soon to be open, many pictures are hitting the web showing all the different things in Taneleer Tivan's collection. We've got a taste of a few of those Easter Eggs in the first Guardians of the Galaxy movie, but a few new VERY interesting things have popped up, particularly Beta Ray Bill's hammer, and some artifacts from Atlantis. Therefore, this leads one to believe that at some point here, we are likely to see both Namor and Beta Ray Bill in the near-term movie future. Maybe, maybe not? For one, there is no guarantee that everything there is canon, even though my guess is Disney intends it to be. Also, just because they may exist in the MCU doesn't guarantee they will show up in the movies. Regardless, it is fun to at least know they exist for sure. This overall would be our first indication of Beta Ray Bill, even though he was rumored to be in GOTG 2, only to be proven as a false rumor. As for Namor, he has been hinted at already once actually during a post-credits scene of I think Iron Man 2 on a Shield World map that had a weird indicating marker of interest in the Middle of the Atlantic Ocean, which leads us to believe that is the location of Atlantis.
It's funny you mention this - Stan Lee was doing an interview this week and stated that there is a surprise character that will debut in Infinity War. He was cut-off by one of his staffers so speculation is rampant that it's one of the two characters you have mentioned.
http://screenrant.com/stan-lee-avengers-infinity-war-characters/
Edit: turns out he made that comment here in Des Moines at Wizard World Comic Con
Speaking at a Q&A in Des Moines, Iowa, Lee told the assembled group, including Gamezone, that a major new character – or characters – will appear in Infinity War. From the sound of it, Lee was then told by his assistant that he couldn’t discuss it any further (shame!) but he did add that fans will be pleased.