This is not true. When Speed Of Sound was first released, it had the largest first week download sales ever, meaning it beat Vertigo. I don't know exact numbers, but it was widely publicized everywhere after it debuted on the Hot 100 at #8.
And in the U.S. anyway, Speed Of Sound was all over the radio when it first came out, just like Vertigo was. I think Vertigo would have made Top Ten at best. But considering that it's been eight years since U2 accomplished that, I think everyone would be ecstatic with that, especially in today's music scene.
As for whether U2 can hit #1 again, it will be difficult. Download sales will certainly help, but that only counts so much to the overall tally. If Speed Of Sound broke all previous download records, as was claimed, and only made it to #8, it would take a lot.