Yes, several teams have moved to FBS. But, there are schools who have since started or re-started football at the FCS level, not too mention teams that had success at the D2 level who have moved to FCS. Among those former D2 schools are South Dakota, South Dakota State, and a school in Fargo, ND named NORTH DAKOTA STATE!!!!!!!!!!!!!! .... All 3 are in the MVFC, and YSU has not yet beaten SDSU since they joined the conference, and has only 1 win over NDSU... YSU did beat SDSU in 2007, the season before SDSU joined the MVFC.
Other teams of note:
*Jacksonville State is a quality FCS program that made the jump from D2 to FCS in 1997
*Coastal Carolina has become a quality FCS program, even though they just started football in 2004.
*Central Arkansas made the jump from D2 to FCS in 2006, and has become a top-tier Southlan Conference program.
*SE Louisiana reinstated football in 2003, after not having a program from 86-2002. This season, SELA was the #4 seed in the FCS playoffs, and won the Southland Conference Title
*Stony Brook just became a full scholarship FCS program in 2007, and is now a member of the CAA. They made the playoffs 2 times while in the Big South(2011 and 2012). In 2012, Stony Brook beat FBS Army, and also won a 1st round playoff game against Villanova. By no means is Stony Brook a top tier FCS program, but they have had some success in their brief time at the FCS level, and being a member of the CAA holds potential for them to develop into a quality FCS program
*Wofford - 1st full season in FCS was 1997. Still remember when they played YSU in 1996 while in probationary status in their move to FCS. I had no idea how to even pronounce the school's name. Woffor plays in the So-Con, and has made the playoffs 6 times from 2003-2012. For those counting, that is FIVE more appearances than YSU over the same time span.
Hard to make the FCS is now "watered down" argument, given YSU's lack of success against SDSU(1-6) and NDSU(1-5) since each school moved to FCS, plus YSU making the playoffs only 1 time in the last 13 years.