District 75 is in Eastern El Paso County. The district is strongly Democratic (during the 2010 election every democrat who ran for statewide office won House District 75). Quintanilla ran unopposed for the seat last year and has easily won re-election in the past (in 10 years in office his worst showing was in 2006, when he received a mere 66% of the vote). The changes to the district's borders made by the 82nd Legislature make it more rural, and slightly more Republican, but there is no reason that a Democrat shouldn't win HD 75 in 2012. Even under the new district lines gubernatorial candidate Bill White still won HD 75 in the 2010 elections (perhaps the most Republican-friendly election in Texas History).
Quintanilla's departure means that there will likely be a new Democrat in the 83rd Legislature. For LGBT Texans that may be a good thing. Quintanilla has a spotty record on LGBT issues. He supported both the statutory and constitutional provisions prohibiting marriage equality and in 2005 voted for an amendment that would have prohibited LGBT people from serving as foster parents. During the 82nd legislative session Quintanilla pointedly stayed out of the debate on efforts to defund or ban LGBT resource centers from Texas State Universities, choosing instead to be "present, not voting."
The only LGBT issue Quintanilla performs well on is anti-bullying efforts. He has historically supported Rep. Garnet Coleman's (D-Houston) efforts to require districts to report instances of harassment or discrimination using an enumerated list that includes sexual orientation and gender identity and expression and voted for both HB 1942 (the "super" anti-bullying bill) and HB 1386 (teen suicide prevention), although neither bill specifically recognized the existence of LGBT students or that they are particularly the targets of bullying.
Quintanilla's unwillingness to support LGBT-specific legislation, or to defend the community from direct attacks, earned him an F on Legislative Queery's 82nd House Scorecard. He actually scored lower than Houston Republican Sarah Davis.
To my knowledge no one has announced a bid to replace Quintanilla. With the district in flux the LGBT constituents of District 75 have a prime opportunity to seek out a friendly candidate and support their bid. The balance of the Texas House is at stake.