The short answer is we don't know.
John's gospel today takes great pains to show that even in his own death, Jesus was in control. It is Jesus who dips the morsel and gives it to Judas. It is at that moment John tells us that Satan entered Judas and Jesus commands him to do what he is going to do, do quickly.
We know that Judas is so contrite that he gives back the money, and so distraught that he commits suicide. Years ago before we understood the human mind, the suicide alone would have been judged a mortal sin. Now we know that the "full consent of the will" required for mortal sin rarely accompanies suicide. And since John makes the point that "Satan entered him", it at least calls into question how much was the mortal sin of Judas.
One thing is certain. John goes to great pains to point out that it is all in God's hands and works together to bring into being the new and everlasting covenant.
Do we know where Judas is at this moment? No. Is there reason to hope he is in heaven? Yes. And if there is hope for Judas there is hope for us all.