It has been the 1900 PF since the resort opened in 1988. The only change I know of is that the entrance is now located off of the main lobby. Originally, the entrance was at the small lobby shared with the Grand Floridian Cafe. BTW, the pre-opening name of the GFC was "Southernaire".
1900 PF has been one of the Floridian's character restaurants since 1988. From GF's opening until sometime in 1989, Flaglers hosted the character breakfast (non-buffet). Prior to the change, 1900 PF only hosted a character dinner.
Some of the character meals featured there include:
Character Breakfast
Flaglers 1988 - 1989 (Fab Five type)
1900 Park Fare
1989 - 98 (Mary Poppins)
1998 - current ?
Character Dinner 1900 Park Fare
Mary Poppins 1988 - 90
Chip & Dales Rescue Rangers 1991 - 93
Mickey & Minnie 1993 - 95
Mickey & Co. 1995 - ?
Disney Villians 8/00 - 7/01
Pooh 7/01 - 1/03
Cinderella's Gala Feast 1/03 - ?
HTH,
Frank