As I think has been said, if it is Brett it is there to stay. It may well get worse with age or can state about the same depending on a lot of things notably cellar conditions. My cellar is pretty cold and I have quite a few old school Rhône’s where Brett levels generally stay the same. But have certainly had other bottles of the same wine with full on Brett blooms.
I think Tempier had more brett issues before Daniel Ravier took over the winemaking (2001?). He replaced a lot of the old foudres used for aging the wines (was done over a few vintages). People still argue about whether it was brett, though.
-Al