I'm not seeing evidence yet that Bohm is a good 3B, but that doesn't mean he can't become one. And Bryant is still a 3B (115 games there in 2019, 16 out of 20 this year). That is less about him as other people on the roster (and the Cubs, like the Dodgers, and the Phillies for that matter, like to move guys around).
Time will tell, we thought Franco was gonna make some all-star teams too. And Brown and Herrera actually did. Bohm certainly seems more likely to hit for a long time. And if he hits like Bryant did in his prime he'll stay at 3B for his prime.