[Anaraxes]

I think you're thinking of the Reflexive Enhancement to turn Warp into a defense, activating automatically without taking a Maneuver. (Concentrate and Ready are prohibited if you're grappled, so this point matters for escaping the grapple.) Even base Warp allows you to use the ability as a Dodge, albeit at a -10 to activate.

The teleporter isn't yet grappled on the very first attack, and so can blink away from that one; the question doesn't apply until after the defense has failed at least once. So, we're talking about blinking away from a followup attack, either from an ally of the grappler, or from the grappler himself.

Just because it seems better to keep a handle on abuse of the power, I'm inclined to say the grapple doesn't break. Grappling someone makes you count as extra encumbrance for them. By that reasoning, the blink would always take the grappler along as well as the rest of the teleporter's stuff, as long as the blinker had sufficient carrying capacity. (Else the blink fails, just as it would if you tried to escape with a ton of gold.) Pile on enough mooks, and they won't be able to teleport away (Reflexively or not). If the teleporter has the carrying capacity, the whole dogpile moves, but relocation in and of itself doesn't make the grapplers let go.

Those mooks are unlikely to be highly trained in Body Sense, so the blink itself can potentially stun them and make them fall down, and likely costs them their ability to act, though they can defend themselves. GURPS "stunning" doesn't mean to go limp and become unable to move, so doesn't seem to break grapples, either. (Perhaps there's a reference in MA or TG that would so state, in which case the teleporters have an improved chance to escape.)