Supernatural's final season includes a whole lot of callbacks to previous seasons - from fan-favorite character returns to episodes reminiscent of the earliest days - but it's also drawing a lot of similarities to the Harry Potter series, particularly the last few books/movies. Whether or not the homages are being done on purpose is unclear, but it's something dedicated fans of both franchises are surely to enjoy.
The two franchises have a lot in common already, of course. The Chosen One(s) fighting evil, averting the end of the world as we know it, monsters and magic and spells, and of course, resurrection - but this season of Supernatural seems to be going over and above to borrow from the adventures of Mr. Potter and the Wizarding World. In particular, the final season of Supernatural has a lot in common with the final books of the Harry Potter series. In this comparison, God is essentially Voldemort, while Sam takes on the role of Harry.
First up, we have the big fight from Supernatural season 14's finale. In an attempt to kill the villain, powerful magic is used - magic that rebounds on the villain and the hero, injuring them both. The villain then disappears, and the hero thinks he is gone for good, but in reality, he's going to come back (bigger and badder than ever). Then, thanks to the shared magical injury that the hero and villain share, the villain is weak, and unable to truly hurt the heroes until he becomes stronger. In addition, the hero starts having visions of what the villain has planned, thanks to their new magical connection. Thankfully, the hero has been learning magic, and even has the ability to resurrect people from the dead (although not often), as well as being part of a trio of friends who will help. However, things may not end well for the Chosen One; thanks to a prophecy/God's plan, that of two people, one must always kill the other (neither can live while the other survives).
Of course, there are a few differences. Sam, unlike Harry, intentionally injured God, knowing his magic gun would rebound on him. The final prophecy/plan is also different - in Supernatural, the pair are Sam and Dean, who God intends to have kill each other. In Harry Potter, the two are Harry and Voldemort himself, which is a fairly big change. But it's hard to miss the obvious parallels, even if that's not a bad thing.
Supernatural has actually referenced Harry Potter more than once (usually when Dean makes fun of Sam for being a nerd), so this story obviously exists in the Supernatural universe. It would be a funny moment if Sam should actually make that connection, and decide to use the Harry Potter formula to kill God - which could fulfill the condition of one brother killing the other, but then see that brother return (just as Harry did after he died in the Forbidden Forest).
Admittedly, the Winchesters already used their resurrection 'stone' for Eileen, but this was explained as single-use because death closes a loophole when someone points it out, and as fans know, Death and the Winchesters have an interesting relationship. She may be convinced to send one back a final time, after all. Of course, these parallels may not pan out, but it would be a brilliant end to the series to see Supernatural tip the hat to Harry Potter, and end with a final reminder that this show has always been about having fun, not just the family business.