***We must remember that Jesus said this before there were any saints and before there was any church.***
What about Abraham, Moses and David (and other Old Testament saints)? Why may these not intercede for you? Do only post-Pentecost believers qualify?
Can John the Baptist intercede? He was killed prior to Pentecost?
John can intercede. He is a saint. We can ask favors from any saint that is in heaven. John is the patron of baptism, bird dealers, diocese of Charleston South Carolina, converts, convulsions, convulsive children, cutters, diocese of Dodge City, Kansas, epilepsy, epileptics, farriers, Genoa Italy, hail, hailstorms, Jordan, Knights Hospitaller, Knights of Malta, lambs, Maltese Knights, monastic life, motorways, diocese of Paterson, New Jersey, Penzance, Cornwall, England, diocese of Portland Maine, printers, Quebec, Sassano Italy, diocese of Savannah, Georgia, spasms, tailors, Torino, Italy Representation
We can ask him to intercede for us to God, along with our own prayer to God. Never hurts to have help from those who died for Him and in Him
I don't ask any of those saints to intercede for me. I can't answer personally. The church, as far as I know, has not encouraged/taught the intercession of anyone other that St. John the Baptist among those you mentioned.
Moses talked to Jesus, and from what I know of the old testament, it was unprecedented, except in the case of I believe it was Saul and Samuel. In that particular situation, Saul went against the established rules by calling up the dead through a medium.