If I have {Master of Etherium}, {Thopter Foundry}, {Sword of the Meek} in play, when I sac sword of the Meek to the foundry, will it re-attach back to the 1/1 flying token when Master of Etherium makes the token 2/2?
No. When the token hits the battlefield, it's a 2/2.
5/1/2007: The triggered ability checks the power and toughness of a creature that enters the battlefield as it exists once it's on the battlefield. For example, Triskelion has 1/1 printed on it, but it enters the battlefield with three +1/+1 counters on it, so it actually enters the battlefield as a 4/4 creature. Sword of the Meek's ability wouldn't trigger. Ditto for a Llanowar Elves that enters the battlefield while you control Gaea's Anthem.