Is the past participle becoming obsolete? (I have went)

I noticed someone saying "I have went" about a month ago and it jarred me. Then I heard it again, and again, so I started paying attention. I noticed that the first couple of people I heard say this were Black, so I figured it was maybe a feature of Afro American Vernacular English. Then I heard a White person say it, and as he was from the South, I figured it was a feature of both AAVE and Southern English. In the meantime, I noticed the same phenomenon with other verbs. Soon I started noticing people from other American regions doing this, people of all colors. Then I began to worry that the past participle was disappearing and when I complained about this to a friend, noticed myself doing it! From browsing around here and elsewhere on the web, I have discovered that "I have went" has always existed. I don't know why I didn't notice it before and I also don't know if my increasing observation of it has to do with my increasing awareness or if the past participle is slowly ceding ground to the simple past form.

What do you think?

I think this is an example of "recency illusion," which you described very well as the situation where "increasing observation" is caused by "increasing awareness."

From one point of view, the past participle could be said to be disappearing. But there are a lot of caveats, and the process has been going on for much longer than any single person's lifetime.

Past tense and past participle forms have often influenced each other or substituted for each other in the history of English. It seems to be easy for this to happen because they both have similarities in meaning, and for regular ("weak") verbs they are identical. There is definitely an overall tendency towards simplification in this area, and it is not confined to any particular region. But this tendency does't always lead to the elimination of the old past participle form; for many verbs it seems the simple past form is more likely to be displaced.

For some verbs, the past participle has already been displaced by the past tense form in at least some varieties of Standard English. Examples are get (where the form got is commonly used as a past participle, although the precise conditions of its use are often complicated), and mow (where the past tense form mowed is commonly used for the past participle instead of mown).

But for other verbs, past tense and past participle are merged only in non-standard varieties.

It's possible that this general tendency, plus influence from non-standard varieties will eventually cause some verbs to have fewer forms in Standard English, but this is by no means inevitable. If it does occur it will be the end result of a centuries-long process.

According to A Social History of English, by Dick Leith,

West Saxon had seven recorded strong verb patterns. An example, fleogan (fly), had five distinct vowel changes in its various tense-forms. As well as a past in fleag, and a past participle flogen, there were vowel changed within each tense: in the present, the form was fliehþ after he, she, or it, and in the past, flugon occurred after plural pronouns. Today, we find that the number of vowel changes has been reduced to three, so we get fly, flew, flown. But in 'non-standard' speech, we often find a reduction to two forms, so we hear I flown it, I done it, etc. Here the past participle form is used for marking past tense.

It is customary, among historians of English when describing the evolution of verb morphology, to attribute such changes to the principle of analogy. [...] We find in recent dialect speech that variation in verb forms is apparently endless, as different strong verb patterns compete with the dominant weak ones. Finally, it is the presence of that two-part weak pattern, present versus past, that may account for the reduction to two forms in the strong verbs that remain.

It is not only in broad dialect speech that the tendency to reduce strong verb forms to two has occured. In my own speech, I have noted hesitations about the past tense of drink; is it he drank, or he drunk? The likelihood is that I will simplify the paradigm by using the past participle form drunk for the simple past drank. Sometimes, however, the process involves the reverse selection: in Jane Austen's narrative, we sometimes find the past tense form used for the past participle, as in the tables were broke up, and much was ate. Thus, the process of simplification used to be as true of so-called educated speech as it is today of dialect. What has happened is that the tendency to reduce the forms of the verb to two has been stigmatized. [...] It was the eighteenth-century codifiers [...] who legitimized such sociolinguistic stratification by insisting that a tripartite pattern in the strong verb was proper and correct from the linguistic point of view. English, like Latin, they suggested, should distinguish between past tense and past participle. The richer the morphology the better; and one grammarian, Lowth, thought it essential to restore inflections, and vowel-alternations, wherever it was possible.

Another relevant paper I found is "The varieties of English spoken in the Southeast of England: morphology and syntax" by Lieselotte Anderwald.

As in many other dialect areas, many speakers in the Southeast have verb paradigms different from the standard. [...] While each verb undoubtedly has its own history, and many non-standard forms may be carry-overs from historical forms that did not make it into the standard, today non-standard grammar is often interpreted as simplifying the StE system. Thus, three-part paradigms are reduced to just two items – although it is not predictable whether the past tense form or the past participle is extended to the other function – and we also often find that two-part paradigms are reduced to just one form, as in the cases of come or run.