Leaving aside the fact that the dead Moses is speaking with Jesus and the OT prophet Elijah is in conversation with the risen Lord
dealing with the text regarding the penitent thief Jesus is speaking in the first person.
The today is not future you would have to make the case Jesus was using a redundant term in this passage in that he only means today he is making this statement, that is eisegesis a sign tradition creeping in and not what is born out of the text.
