No. Once the ability resolves, the creature gets +1/+2 and that's that. You can do whatever else afterwards.
If it went away if the creature stopped being a 1/1, it would cause itself to be useless since once the ability resolved, it was a 2/3 not a 1/1.
August 30, 2014 9:56 p.m.
If you used Wings of Velis Vel on a creature after Pendelhaven 's ability has resolved on that creature, the creature will be a 5/6. No matter what order they begin applying in, power and toughness increases always apply after things that set power and toughness to a specific value.