Since the news that Disney may be purchasing 20th Century Fox, Marvel fans everywhere have gone into melt down at the prospect of the likes of The Fantastic Four and The X-Men joining Cap and Iron Man in the MCU.
While fans have every reason to be excited, if these characters are to reach their full potential under the Disney umbrella, it won't be as simple as introducing them all immediately. With dozens of heroes already populating the MCU, fighting for screen time where they can, Marvel has to strategically integrate these newbies to allow for maximum development, and to give them the time and attention they deserve.
Marvel have balanced their enormous roster expertly since the beginning of the MCU, though not perfectly, with a handful of characters not being able to live up to expectations or potential. With these former Fox properties finally making the leap into the MCU (hypothetically at this point), there is a lot pressure on Kevin Feige and Marvel to get it right, and do everyone justice.
All this begins with how they are brought into the Universe in the first place. While the timing has to be perfect, the introduction of these characters also has to make sense within the wider story of the MCU.