No, wild shape does not automatically break the grapple.
Grappling applies the 'grappled' condition and conditions are not automatically removed when you wild shape.
Further, once you have the grappled condition, the restrictions on grappling target size does not matter. Only the listed ways under the condition's description, the grappler releasing the grapple, or 'escaping the grapple' will remove the condition. (PHB pg. 195).
From PHB Appendix A (pg 290)
Grappled
- A grappled creature's speed becomes 0, and it can't benefit
from any bonus to its speed.
- The condition ends if the grappler is
incapacitated (see the condition)
- The condition also ends if an effect
removes the grappled creature from the reach of the grappler or
grappling effect, such as when a creature is hurled away by the
thunderwave spell.
For wild shaping into a larger creature than the grappler, unless the grappler has the 'grappler feat' (PHB pg 167), which tell us that creatures larger than you automatically succeed escape attempts, you can use an action and automatically escape from the grapple.
The spell does what it says it does, and the condition (Grappled) does what it says it does. Victor is flung 10'.
The spell moves Victor 10'. Clear enough. Unless something would stop that movement.
The condition doesn't cause Victor to be immobile, it reduces his speed to 0'. He's not nailed to the floor or encased in carbonite, it's just hard for him to move of his own volition. Grab someone by the wrist with both hands: you've got them Grappled.
So, since nothing in Grappled says Victor can't be moved by an effect (and, in fact, as you mention it specifically mentions this effect as one that can move the victim out of the grappler's grasp) and the spell says it moves Victor, that's what it does.
As long as the effect of Thunderwave ejects Victor from Gary's reach, Victor is no longer grappled.
(As @MartinCarney rightly points out, if Gary's an Otyugh, even 10' may not escape Gary's reach!)
Best Answer
From the Grappled condition in Appendix A of the Player's Handbook or Player's Basic Rules:
So if you use Blink and vanish into the Ethereal Plane, the grapple will end. Obviously if you use Blink and don't vanish into the Ethereal Plane, the grapple will keep going until you do.