If U2 play Sometimes, it would be one of the biggest blunders in Grammy and U2 history.
That should be for next year's Grammy already so that the song will win song of the year and record of the year. If they play it this year, when the song isn't nominated or the album isn't qualified yet:
1. Grammy execs will think U2 are selfish and opportunistic, trying to make the Grammy awards their own springboard to publicize their new single when Vertigo should have been appropriate.
2. Grammy execs won't nominate the song next year because "well, U2 already played it last year so if we nominate it this year and let it win - they'd look crazy playing the same song for two years or to not play their song that won --- so let's not nominate them to save the trouble"
3. The Grammies should showcase the nominated songs, so the entire world and the music critics will know how good/bad the tastes of the Grammy execs are.
4. Vertigo, being 3 minutes long, is perfect for those Grammy awards because every second counts in an awards show like that to favor the advertisers who have paid big bucks to get slots. Sometimes is way too long, and if they cut it short, it would lose much of its power.
If they play Sometimes in this Grammy, it will be a blunder of the greatest proportion and will virtually guarantee them getting the cold shoulder in next year's Grammies.
Cheers,
J