No, in a microburst encounter, if you're experiencing a tailwind, you're in the outflow, and decreasing performance. As you fly out of the shear effect and begin to recover, you're doing so from a very slow condition. If the airspeed is increasing from that point and you're approaching Vmo, then you're certainly not flying the airlplane (it's flying you), and you're far out of danger. Time to either convert that extra thrust into a climb rate or get the power pulled back. Exceeding upper speed limitations during a windshear encounter, unless you were right on the edge of Vmo/Mmo at the outset (not particularly likely...and wouldn't require additional thrust if experiencing an excursion above your speed limits)...you're not going to go there when you're pitching for the shaker.