No.
At least 6 months.
Even in its Early Access phase, Path of Exile 2 is a substantial game. It features an extensive campaign spanning three acts and a robust endgame.
When you purchase your first supporter pack that includes an Early Access key, the key will be automatically redeemed on the account used for the purchase. There's nothing else you need to do—just download the game client when it's available and log in on launch day!