It's an interesting situation for the various ways it can play out but realistically
Undertaker is winning
Once you've established that fact, you've got the matter of how HHH loses.
Clean - In which case you've nowhere to go with the story
Unclean - Shawn's involvement
Now this is complicated because I don't see a clean finish but at the same time, Shawns involvement would in almost all circumstances require him to come out of retirement. And so another 2 possibilities spring up
Shawn costs HHH the match, ends his kayfabe retirement and we get the return of HBK.
or (and this is where I think it's heading)
Shawn puts HHH out of his misery. If you can imagine this match being an absolute war with HHH being destroyed but refusing to lose, I could imagine Shawn putting the final nail in his coffin as an act of mercy and the last words HHH would hear before HBK kicks his head off are "It's time"
Undertaker is winning
Once you've established that fact, you've got the matter of how HHH loses.
Clean - In which case you've nowhere to go with the story
Unclean - Shawn's involvement
Now this is complicated because I don't see a clean finish but at the same time, Shawns involvement would in almost all circumstances require him to come out of retirement. And so another 2 possibilities spring up
Shawn costs HHH the match, ends his kayfabe retirement and we get the return of HBK.
or (and this is where I think it's heading)
Shawn puts HHH out of his misery. If you can imagine this match being an absolute war with HHH being destroyed but refusing to lose, I could imagine Shawn putting the final nail in his coffin as an act of mercy and the last words HHH would hear before HBK kicks his head off are "It's time"