No, He will not "celebrate Mass". He is the Lamb that was slain. He is returning (the Parousia) in glory at the end of "time" (okay we could discuss this for months lol) to establish a "new Jerusalem": i.e., a "heaven on earth". All things will "pass away" doesn't mean they are sent to the trash. God doesn't make trash, and everything is part of Him. It means it will be a "resurrected' creation, restored to its original nature (Eden). At least, that is what I have been taught. What I KNOW is that God is very, very hesitant to lose one soul, wants all to be with Him, and will never turn His back on anything He created but, rather, restore it to perfection. I could be wrong, I often am.