Promoters of Garcia (Golden Boy) and Davis (Mayweather) won't let these two fighters meet this early in their career. They'll play their cards and milk as much money as they can from their fighters. It will probably take five more years before that fight happens provided they remain undefeated or they still keep a good record.
We've seen these delaying tactics happen before with Pacquiao-Mayweather and Alvarez-Golovkin.
If Garcia already accepted the terms to fight Campbell, then its him that he should fight.
They don't need to remain undefeated to face somewhere down the line and make big money.
I personally think Garcia beats Gervonta if they were to fight sometime soon. Davis is like a small version of Wilder, he's got power but not much else.
But either way, if Garcia ends up fighting Campbell (who he'll beat), then he'll have to challenge Loma. And Loma will obviously destroy Ryan Garcia, causing him to lose his undefeated record.
The only way they can avoid this is by pushing back the Loma fight as far as they can, and hoping he gets injured and/or slows down (which he might). He's 32 now so he probably only has 2-3 more good years in him.
The most optimal scenario would be fight Campbell now, delay Loma fight, fight Davis, then go for the titles against Loma for a massive pay day.