The lands affected by Sylvan Awakening stop being creatures as your next untap step begins, before you untap your permanents. If this causes any state-based actions to become applicable, or if any abilities trigger, those are handled during your upkeep.
Sylvan Awakening doesnâ€™t untap any of the lands that become creatures.
Sylvan Awakening affects only lands you control at the time it resolves. Lands you begin to control before your next turn wonâ€™t become creatures.