Does God already know, right now,
who will go to heaven?

Yes. The Bible is clear that the all-knowing Creator God, knows the end from the very beginning. Nothing sneaks up on God and takes Him by surprise.

I make known the end from the beginning, from ancient times, what is still to come. I say: My purpose will stand, and I will do all that I please. — Isaiah 46:10

Salvation is clearly God's plan and purpose, and He worked it out from before the creation of the earth...

Praise be to the God and Father of our Lord Jesus Christ, who has blessed us in the heavenly realms with every spiritual blessing in Christ. 4 For he chose us in him before the creation of the world to be holy and blameless in his sight. In love 5 he predestined us to be adopted as his sons through Jesus Christ, in accordance with his pleasure and will- 6 to the praise of his glorious grace, which he has freely given us in the One he loves. 7 In him we have redemption through his blood, the forgiveness of sins, in accordance with the riches of God's grace 8 that he lavished on us with all wisdom and understanding. 9 And he made known to us the mystery of his will according to his good pleasure, which he purposed in Christ, 10 to be put into effect when the times will have reached their fulfillment-to bring all things in heaven and on earth together under one head, even Christ.

11 In him we were also chosen, having been predestined according to the plan of him who works out everything in conformity with the purpose of his will, 12 in order that we, who were the first to hope in Christ, might be for the praise of his glory. 13 And you also were included in Christ when you heard the word of truth, the gospel of your salvation. Having believed, you were marked in him with a seal, the promised Holy Spirit, 14 who is a deposit guaranteeing our inheritance until the redemption of those who are God's possession-to the praise of his glory. — Ephesians 1:3-14

Revelation 17:8 also speaks of "inhabitants of the earth whose names have not been written in the book of life from the creation of the world." God knows your heart here and now and how it will be every day of your life. God knows every person, for all time, who will believe or refuse to believe in Him — and He has all along, even before Adam and Eve were first given breath. The good news is that in foreseeing salvation, He planned the means before the creation of the world as well...

He [Christ] was chosen before the creation of the world, but was revealed in these last times for your sake. 21 Through him you believe in God, who raised him from the dead and glorified him, and so your faith and hope are in God. 1 Peter 1:19-21