It has to be that Vero turns into a total Bridezilla way before anything is even set in stone, forcing Arch back to the obvious.
UNLESS...
Archie's ultimate chosing of Veronica opens the door for Jughead to finally profess his undying love for Betty. Feeling jilted and willing to do anything to ruin Archie's life (because most men want both women to equally want them) she goes for it. Betty then realizes that she and Jughead had many things in common the entire time and live happily ever after.
Meanwhile Archie gets into Veronica's family business and becomes a pissant under her father's thumb while she spends most of Archie's hard earned money paying off her boy toy(s) that satisfy her since Archie's too stressed to even get it up. He's miserable and wishes every day that he'd chosen Betty.
Betty wins.