Did you ask for some "plausible" old songs that might get played, or for the old songs we want to hear?
I want to hear live October, it's no challenge for Bono, nowadays he is capable to play it! And some of the more obscure War stuff would be great (Seconds, Surrender, Two Hearts...), but I think they are thinking to play less and less old songs... IWF, Out Of Control and Electric Co will keep appearing until they quit. The rest? Well.............
I'd love to hear Seconds, it's still my favorite Edge song, or maybe Two Hearts Beat As One, but the older U2 songs I'd like to hear more of are a little more recent.
Lemon, Daddy's Gonna Pay For Your Crashed Car, Love Is Blindness, Ultraviolet (Light My Way), Numb, Zooropa, Tryin' To Throw Your Arms Around the World, Even Better than the Real Thing, Dirty Day, MoFo, Do You Feel Loved, Miami, Discotheque/If You Wear That Velvet Dress, and Last Night On Earth have been completely cast by the wayside.
The early material saw lots of play because of the years it all filled the setlists, but the stuff from the ZooTV/PopMart tours were discarded once they had served their purpose. These live gems need to make a comeback, even though they aren't ancient, just old.
Last Night on Earth is a live gem, a pure rock song. Discotheque for the 2 nights it was on the Vertigo sounded awesome, but i read the band didnt think so. I just hope when they tour again they continute with the diversity in the setlist and maybe even throw in some surprises