It's looking like a closer division race than last year, however, two of your assumptions in here may not be fair.
One, I'm not sure they can expect O'Neill to come back and produce at last year's pace. Before he went on the IL last month, he was among the worst position players in baseball at a -0.6 WAR. Even his defense was below his Gold Glove level from last year. He is a guy who has always had a huge hole in his bat, consistently ranking among the league leaders in K% and Whiff%. He had a great season last year for sure, mainly because he was able to hit the ball extremely hard when he did make contact, but the same warning signs were still there as he ranked in the 4th percentile in both K% and Whiff% (i.e., Keston Hiura territory). Fast forward to this season, and his hard hit rate has completely dovetailed to the point where he is no longer able to offset his huge swing and miss propensities. So, unless he suddenly starts making contact more consistently, it is highly unlikely that he will ever be able to repeat or come close to the season he had last year.
Two, while you're correct in that Gorman, Donovan, and Yepez have come up and provided them with a big boost on the offensive end to help make up for the injuries/disappointments in O'Neill, Carlson, DeJong, and Sosa, I'm not sure if they'll be able to count on them to continue to produce at the level they currently are. None of these guys were "can't miss prospects" like a Vlad Jr., Franco, or Julio Rodriguez. Gorman was the only one who ever made a top 100 prospect list, and like O'Neill, he comes with huge questions in terms of his ability to make contact. So, while Gorman currently has a .950 OPS, the more at-bats he gets this season we can expect that to decline significantly due to his 34.6 K% and pitchers adjusting how they pitch to him. As for Yepez and Donovan, who both never sniffed top 100 prospect status, Yepez's production has already begun to steadily decline after a hot start upon his initial call-up, and while Donovan's K/BB ratios are promising and he possesses an above-average hit tool, his .855 OPS is unsustainable due to his lack of power and he has below-average tools everywhere else. Now, I'm not questioning that these guys could all wind up becoming good major league players (and perhaps even something more in Gorman's case), however, I think we can say with near-certainty that they won't continue to combine for an .870 OPS over the remainder of the season.