I can't honestly imagine -anyone- thinking it was いまび ever (though apparently you know some such people). However, きょう is one of the first irregular readings taught, if not -the- first. I don't know who would learn the phonetic change patterns before common irregular readings, so I would expect people to read it as いまひ (not び) if they tried to put a kun-reading to it at all ... although another thing usually taught very early on is that most compounds are ON-readings making こんにち and こんじつ more likely, and they aren't even completely wrong, just not the intended reading for most modern contexts. If you haven't learned to differentiate ON and kun readings, then I'd think いまにち ... にちようび and いま are in the first 100 words learned for most people, after all.
