Steven mentions that his sister Hayley was giving the coach a Rod Carew in the parking lot. Rod Carew was a Major League Baseball player for the Minnesota Twins and California Angels in the 1970s and 1980s. In addition to being the only major leaguer to ever be born in a train, he was one of the most prolific hitters of his generation. It should be noted that Steve is using R"od Carew" as rhyming slang for "screw".
I really like the idea of using time travel and alternate timelines to streamline both universes. But they can erase X1 also while they are at it. Or it could just be the McKellen and Stewart are in the beginning or end looking back at the story.