Steve/Tony's never happened*, I make a point of checking every year lest the hated Zarabithia be vindicated. The others are bound to.

(Will be intrigued to see if EMH breaks the streak this year. Ditto JL/JLU for Clark/Bruce. SMH at that one.)

*There's one weird crossover and two many fandom mashups it's mentioned in, but all have YT number hits, they weren't straight up Stony that MCU fans would have wanted to/did read.