I've mentioned before that my father was a printer. I learned a number of things about printing because of that (I talked about the California Job Case in my post about mnemonics). One printing-related thing I learned, which many people learn in other ways, is “ETAOIN SHRDLU” — the twelve most common letters in printed English, in decreasing order of frequency. We used to pronounce it "eta-oyn shurd-loo".
I don't know whether they consider slang when they come up with such frequency distributions. If so, ETAOIN SHRDLU might be nearing the end of its life.
Slang used to be mostly a spoken phenomenon. People didn't do casual writing very much, and when they did they tended to be more formal than they were when they spoke. And so it didn't matter much how slang words were spelled, and apart from made-up slang words (like “copacetic”), most were spelled just as one would expect. When we used “dough” and “bread” to refer to money, we spelled them just as a baker does, and when “bad” took the slang meaning of “good”, it was still spelled B-A-D.
On the Internet, those coining and using slang are writing it as much as or more than they're speaking it, and how it's spelled (and capitalized) is significant. This does somewhat pre-date the Internet explosion — “phat”, meaning good, dates to the 1960s, and you have to spell it that way because “fat” just means, well, fat. But with informal writing on the Internet, in email, instant messaging, blogs, and so on, and text messaging on phones, what I'll call “orthographic slang” has mushroomed. There's a whole new wave (or let's write it “2u4\/3”) of spelling oddities that, if they stay around and get counted, could make some dramatic changes.
When your computer has been hacked, by a “haxor” (or “haxxor”), you have been “ownd”, and the haxor “ownz” you (or “pwnz”, because the P is next to the O on the keyboard). If he pwnz enough people, he is “teh haxx0rz!” And that might well send him ROFLHAO. The slang language, “leet”, is itself slangly spelled “l33t”, or sometimes “1337”.
What does this do to the supremacy of the E? If half the E's are replaced by “3” or eliminated entirely, that probably throws it out of the top twelve. X and Z are clearly moving out of dead last, and, indeed, if Z is prefereable to S for forming plurals (“boyz”), possessives (“ourz”), and verbs (“ownz”), it will surely move up to at least sixth place.
For the 21st century: 37104Z WNXRLQ
You figure out how to pronounce it.