Since the start of the MCU, Marvel fans have been speculating on ways to bring the larger Marvel universe. With the Fox / Disney merger moving forward at full steam, that dream is becoming a reality. One thing we don't know if how Kevin Feige and his team will lay down these future foundations.
Thanks to an eagle-eyed Reddit user (u/kobikwahbz) we may have our first in-universe clue towards their inclusion. The post points out a detail hidden on the Avenger's time travel monitor. There is a "Quantum Vectors" section of the screen that seems to act as a history of time locations they have been to and/or search history of times they are interested in. Three years are listed in this top right-hand corner of the display: 2009, 2012, and... 2988?
You have to question why those years.
2012 makes sense: it is obviously the time stamp for the first Avengers throw-down where Professor Hulk tried so poorly to blend in with his aggressive former self. 2009, while not explicitly tied to anything could be an Easter Egg nod to Tony's announcement that acted as the first half of this saga's bookends. The times line up. He had been Iron Man for about 6 months at the start of the second film that released May of 2010. Around the same time as that famous "I am Iron Man" announcement, T'Challa was given the Black Panther mantle and Bruce was starting his research in South America. All these events are what kicked off the MCU. Seems like an honorable nod to the time that pushed this universe into existence.
2988 is quite the anomaly though.
While there is perhaps a fair bit of conjecture on the 2009 date, there is nothing that we know of in the current MCU that takes place so far into the future. The closest we've come is seeing Spider-Man 2099 in the "Into the Spider-Verse" end credits scene a few hundred years and a multiverse away from the current MCU. So why have the date there? One thing we have learned from Marvel films, Kevin Feige, and especially the Russo Brothers is that even the tiniest detail is planned out. Easter eggs are hidden everywhere and like an army of bunnies high on egg dye, the Marvel team is looking at the future and leaving clues behind.
There is an important use of the number 2988 in Marvel's comic history. Just like the new show coming to Disney +, Marvel comics has a long-running series of "What If" comics that explore alternate dimensions and timelines to play with characters in ways that would upset our fandom hearts if it was done in a mainline's continuity. Things like, "what if the Punisher was a hall monitor in a school for superpowered kids" or "Thanos joins the Avengers" or "didn't die", again. These stories have traditionally been their own side thing and are rarely connected to the greater stories going on. But what if they are using one of these stories as a clue to the addition of Fox property heroes in the MCU?
Because Earth-2988 was shown in "What If" issue #111 - Wolverine: Horseman of War. So, what if the "What If" series will aid the introduction of X-men and the Fantastic 4 into the MCU?
Yes, this is stretching things way further than with the 2009 analysis, but maybe they are cluing us into the existence of mutants and hinting at the arrival of these characters in a less than friendly way. This comic followed Wolverine as he killed all the other heroes in the Marvel universe. So, assuming this is a reference to our metal bone plated, hairy Canadian friend, why would Marvel include this in Endgame? What connection would this have to this epic story? Perhaps we are about to see the ground work laid for a battle between earths mighiest heroes and the most powerful school of mutants. This could be a reference to the greater Marvel universes and the inclusion of X-men into the MCU.
Alternatively, of course, it might just be a reference to the First Battle of Svartalfheim, which happened in 2988 BC.
If you look closely at the image from Reddit, there are markers next to the years that seem to indicate BC and AD. 2988 is the only one that does not match the AD marks of the other two. When diving further into the lore of Marvel and looking for solid MCU connections, I realized this date matches the legendary battle mentioned in Thor the Dark World when Asgard defeated the Dark Elves and Malekith. This actually matches up quite nicely with scrapped plans to have Thor and Tony go to Asgard. Stephen McFeely and Christopher Markus, the screenwriters for Avengers: Endgame, shared in an interview with Fandango that they "like the idea of Tony going to Asgard and seeing science versus magic." This was adapted to the battle of New York later in production.
Considering Endgame is the culmination of a rich history told over the last 11 years of Marvel movies, it is fitting that this tiny detail points back to the oldest recorded event in the MCU.