In a recent interview with Yahoo! Movies, the Russo Brothers said that the Silver Surfer is not in Avengers: Infinity War. They could, however, have him appear in a later film.
Here is the exact quote from Joe Russo:
I don’t think we own Silver Surfer, but it’s fan-wish fulfillment and, you know, if this Disney-Fox deal goes through there’s going to be a lot more characters coming into the Marvel universe, so some of those crazy fan theories might come true.
This quote tells us two things. The first is that there is no Silver Surfer cameo in Avengers: Infinity War. The second is that the Russo brothers could see the character join the MCU later (if the FOX deal goes through).
It is also likely that Kevin Feige, the mastermind behind the Marvel Cinematic Universe, has done some work, planning the appearances and introductions of characters into the MCU who were previously in the possession of 20th Century Fox. These characters include the Fantastic Four, the X-Men, Doctor Doom, and the Silver Surfer.
In the comics, the Silver Surfer was an alien who saved his planet by becoming a herald of the world-eating god Galactus. He battled the Fantastic Four, who helped turn him good again and defeat Galactus. His character is much more present in cosmic events in the Marvel Universe (MU) and with the MCU delving deeper into the cosmic realm from the comics, the presence of the Silver Surfer in Phase 4 or beyond is fairly likely.
The character also appeared in The Fantastic Four: Rise of the Silver Surfer as a villain-turned-hero, similar to events of the comics.
Source: Yahoo! Movies
Avengers: Infinity War releases in theaters on April 27th.
Avengers; Infinity War– Iron Man, Thor, the Hulk and the rest of the Avengers unite to battle their most powerful enemy yet — the evil Thanos. On a mission to collect all six Infinity Stones, Thanos plans to use the artifacts to inflict his twisted will on reality. The fate of the planet and existence itself has never been more uncertain as everything the Avengers have fought for has led up to this moment.