What Ohtani has done is nothing short of incredible and (as Babe Ruth was never really both a pitcher and a full time position player) and unprecedented.
Don't be surprised if we end up seeing more of this down the road. Bobby Thigpen was the best pitcher on Mississippi St's national championship team in the mid 1980's and was also their best hitter (and center fielder when he wasn't pitching). That team also had future MLB all stars Will Clark, Rafael Palmeiro and Jeff Brantley. Once his college career ended the White Sox made him a full time pitcher. It is very common that in lower levels, the best pitcher is also one of the best hitters, it had always been the common belief that at some point they have to give up one for the benefit of the other and as most pitchers do not get at bats in minor league ball (universal DH for decades) they cannot maintain their skills as a batter.
Something similar happened about four decades ago. It had been common belief that being a middle infielder was additionally taxing mentally and could impact a batters performance. Additionally, it was easier and quicker to advance through the minor leagues as an outfielder than it was as a middle infielder due to the shorter learning curve. Many hall of fame outfielders (Joe DiMaggio, Willie Mays, Mickey Mantle, Henry Aaron, Carl Yastrzemski among them) were moved from shortstop (second base in Aaron's case) to the outfield early on in the minor leagues on the belief that a) they would make it to the big leagues much quicker and b) they would be better hitters in the long run as outfielders. Ernie Banks was an exception but it wasn't until after Robin Yount's success (which took about five years in the majors before he was able to hit consistently for both average and power) that the gates were opened for players like Ripkin, Rodriguez, etc. Two thIrds (or more) of the shortstops from the mid 90's forward would have been moved to the outfield in low minor league ball if the common belief hadn't changed.
I imagine that by the end of this decade we will see a handful of pitchers who will also be every day players (even if it is as DH) and this number will grow in time.
That said, it may take decades before we see guy who will be both one of the top pitchers and one of the best power hitters in the game. He is something special.