Regarding Barkley's chances of having another chance at the rushing record next year - the performances of the previous eight RBs in the season they had over 2,000 yards rushing and the following season are listed below:
O.J. Simpson: 1973 - 332-2003-12 (6.0 avg) 1974 - 270-1125-3 (4.2 avg)
Eric Dickerson: 1984 - 379-2105-14 (5.6 avg) 1985 - 292-1234-12 (4.2 avg)
Barry Sanders: 1997 - 335-2053-11 (6.1 avg) 1998 - 343-1491-4 (4.3 avg)
Terrell Davis: 1998 - 392-2008-21 (5.1 avg) 1999 - 67-211-2 (3.1 avg)*
Jamal Lewis: 2003 - 387-2066-14 (5.3 avg) 2004 - 235-1006-7 (4.3 avg)
Chris Johnson: 2009 - 358-2006-14 (5.6 avg) 2010 - 316-1364-11 (4.3 avg)
Adrian Peterson: 2012 - 348-2097-12 (6.0 avg) 2013 - 279-1266-10 (4.5 avg)
Derrick Henry: 2020 - 378-2027-17 (5.4 avg) 2021 - 219-937-10 (4.3 avg)**
(Figures taken from Wikipedia, using the 2,000 yard club page as a starting point.)
- Davis played only 4 games in 1999 due to a serious knee injury.
** Henry played only 8 games in 2021 due to a foot injury.
These are just the bare statistics, and I haven't looked into the context of any of these players in the following season (e.g. if there were changes to the offensive personnel or coaching staff) other than to note where the player missed most of the following season). Given that each of the previous eight 2,000 yard rushers had a significant drop-off in production the following season, though, it seems likely that Barclay will not reach the heights of 2024 in the 2025 season.