I would agree.
If as in "one last hurrah" you mean a glory battle of mandos against the old sith, that isn't too far out of the realm. Possibly since the mandalorians (especially Canderous himself) actually knew about the sith empire that lurk beyond I would say that is ample motive for the Sith to want to eliminate him.
Seeing as how he (Mandalore) lusted for battle, and wanted to follow in the wake of Revan and possibly later the Exile, that would support your theory.
Suppose, there were sith militia who had not gone into stasis or sealed themselves off from the galaxy. A satellite war could have been staged, moved, and put into play in the outer rim. Out of reach in the old republic yet far enough away from the empire so as to not be discovered. Or perhaps Mandalore had rejoined his Jedi allies. Or maybe since the Republic was not paying attention to the Mandalorians, something outreaching from beyond started a war with the mandalorians alone and it went unnoticed by the rest of the galaxy. There are many possibilities as to what really could have happened.
What we do know is that somehow the Mandalorian leadership appears to be usurped by the sith, or so the republic intelligence would indicate as told by the chronicler.
Considering, too, that by TOR's arrival the mandalorians were supposedly fighting on the Sith side, it would seem to imply infiltration or corruption overtook the mandalorians as a whole, but that there may have been some who do not agree with the Old Sith and fight at least for their own survival if not the Republic.
I invite conjecture or debate on any of these points.