Asked whether Teixeira's deal was for the full year, Trident's official Twitter account responded: "It is still not confirmed."
Ceccon also tweeted after the announcement, but only to say that "Now is official so I can say that I will not do the #hungarygp with @trident_team in @GP2_Official."
The Hungaroring hosts the seventh weekend of the 2013 GP2 Series championship, with rounds in Belgium, Italy and Singapore to follow before the season finale in Abu Dhabi on November 2/3.
Practice for this weekend's race is scheduled for 12 noon (11am BST) on Friday, with qualifying following the conclusion of F1 Free Practice 2 at 3.55pm (2.55pm BST) later the same day.
The 37-lap feature race will start at 3.40pm (2.40pm BST) on Saturday afternoon following F1 qualifying, with the 28-lap sprint race getting the green light at 10.35am (9.35am BST) on Sunday morning.