Thats the problem, the Panther Mafia sees the D3 as its replacement, which it is not.
Its not directly replacing it, it just happens to be the replacement since the CV is no longer sold retail. Much like the MKS is the Lincoln flagship, just because its the most expensive Lincoln.
As for its replacement, the Panther is WAY OVER DUE FOR A REPLACEMENT! Nearly every other car in Ford's lineup has been replaced after 10 years or so. The only other car platform that stuck around too long was the old Mustang Platform and that was partly due to bad idea in making it a FWD car in the late 80's (which the old platform outlasted!) and then it getting updated in 1994, more so then the Panther ever was in the past 30 years.