So if my calculation are right we have :
504928.00786310 btc linked which will bring approx. : 31,558 gb
and we have 255,492gb in circulation which will bring : 51,098 gb more after airdrop
So
31,558+51,098= 82,656 new gb added to the one in circulation which in total will bring to 338,148 gb in circulation.
Yes that's 1/3 of all gbytes.
Yes i think in this rate we will have at least 3 more airdrops.