The Marvel Cinematic Universe has never delved into R territory before (unless you count the harder-hitting Defenders content over on Netflix), so that could raise some issues with the process of bringing Blade to life in a way that makes sense and honors his legacy.
Having said all of that, the possibility of Blade entering the Marvel Cinematic Universe would have to face some major hurdles if it ever wanted to become a reality.
Chief among these concerns is the fact that a new film version of Blade would likely need an R-rating to appease die-hard fans of the character.