The Rays have been doing this for the past 10 or so years now. They have been basically just churning out prospect after prospect and then trading them once they are close to FA.
It may not work exactly 100% of the time but the Brewers only need to be successful once or twice. Basically they need to keep on developing MLB talent which they have been able to do recently with Mitchell, Wiemer and Turang. Then make trades for players like Adames and Urias when needed.
Pitching is always the hard part and no team in MLB has really got this consistently correct. The Guardians and the Rays have been the best but it is not perfect and they have hit some bumps here and there on their players.
The Brewers definitely believe they can trade their players and continue to be successful without going through a full on rebuild like the Orioles and Cubs have done. The Cubs problem after they trading their superstars away they didn't have anything in their farm system it was completely barren. The Cubs went scorched earth tactics on their farm system to win a World Series. They won one but they absolutely destroyed their farm system in doing so. This is why the Cubs are stuck in mediocrity right now and it is something the Brewers are trying to avoid.
I think the Brewers want to keep their payroll on average around $90-100m which allows them to go over when needed. Top players normally bring over AA or A+ level prospects. I don't see the Brewers trading Burnes, Woodruff or Adames for players below A+ at least not the main piece(s) coming over. The headliner in a trade for Burnes or Adames will more than likely be a player in AA which means that player normally is only one or two years away at most.
So yes the Brewers are still thinking they can compete even after trading Burnes, Woodruff and Adames.