Discover Magazine has a neat little article on irregular verbs that doesn't seem to be online:
Now for frustrated English-language students everywhere, there is good news: a formula that predicts hwen an irregular verb will convert to the regular form. However, they might have a long wait.
Derived by Harvard University mathematician Erez Lieberman, the formula shows that verbs have their own "half-life", that is, the time it takes for half of the verbs in a particular group to become regular. The half-life is based on how popular a verb is: the more often it is used, the longer it will take to convert. For example, the verbs have and hold both have irregular forms in the past tense--had and held. Yet have is used roughly 100 times more often than hold. In line with that, we should expect held to become holded in nearly one-seventh the time (in about 5,400 years) it will take for had to become haved (in roughly 38,800 years).
To come up with the formula, Liebrman compiled a list of 177 Old English irregular verbs, many of which had regularized. He grouped them according to how often they popped up in modern English, which correlated with how long it took for the irregular forms to disappear.
The next irregular verbs likely to fall include infrequently used ones like slink.
I suppose in the beginning, all verbs were irregular. Which suggests that we're falling from an Edenic garden of plenty towards a monotonous, sanitized future in which all the verbs are exactly alike. Paging Rod Serling . . .