While most of the people who won elections in November take office in January, Judge Luis Aguilar will likely take office sooner than that date.
Its a unique situation because Aguilar's seat was the unexpired term of another judge who still had a couple years left on his term. Governor Rick Perry appointed Judge Bill Hicks to fill the position and according the the Texas Constitution, the appointed judge serves until the next general election, which is why the office was on the ballot in this election cycle, this election cycle being the next general election.
So since the election took place on November the 6th, it appears that Aguilar was able to take over the seat on the bench following the states' official canvassing of the vote. That is typically held 30 days after the election.
Which would be today.
Its still unconfirmed but it appears that Aguilar is required to take office today under the Texas Constitution. The seat will be up in again in two years in accordance with its regular term cycle.