I totally disagree.
I'm not saying it's a sure bet that Mookie tops the 30th best WAR ever put together since 1925, but he's still under prime age and has clear areas where improvement can be made- like swinging at more good pitches, instead of taking so many.
History shows us that many of the greatest seasons of all time were later topped by the same player, or at least they came very close to topping it. I won't use Bonds as an example, but here are a few others I found:
While Ted Williams was a freak of nature, and he had so many great seasons, he nearly topped his alltime best (1.287 in 1941) 16 years later! In 1957, he hit 1.257, when he was way past prime.
Babe Ruth went off the charts in 1926 with a 1.253 OPS- an OPS so high, it had to be a once in a lifetime thing, right? Well, the very next year, he topped it.
Mark McGwire totally smashed his best OPS in 1996 by hitting 1.198.Two years later, he topped it.
Mantle topped 1956 in 1957.
Jimmie Foxx nearly topped 1938 in 1939.
Hornsby topped 1928 in 1929.
Musial topped 1946 in 1948.
Sure, when you look at the list of the best OPS seasons of all time, there are plenty of players only seen once in the top 50, 100 or 200. One and done, yes, but even the Hack Wilsons, Frank Rhomases and Jeff Bagwells of the world had several fantastic seasons not far removed from their best.
It's not absurd to think there's a "good chance" Betts can repeat or do better at least one more time.