There is … some disagreement as to what to call abbreviations that some speakers pronounce as letters and others pronounce as a word. For example, the terms URL and IRA can be pronounced as individual letters: [ˈjuːˌɑrˌɛl] and ['ɑɪˌɑrˌeɪ] respectively; or as a single word: [ˈərl] and ['ɑɪˌrʌ] respectively. Such constructions, however—regardless of how they are pronounced—if formed from initials, may be identified as initialisms without controversy.Sorry for bringing up the issue of IRAs if you're giving any thought to retirement, but, hey, it's data. If you think about how these forms might change over time, you might expect them to become more word-like, especially as people forget what the initials stand for. That is, you might expect IRA to start out life ['ɑɪˌɑrˌeɪ] and become ['ɑɪˌrʌ], keeping the wiki-transcription as was.
But there seem to be a couple of examples of the reverse. Through college and grad school, Reserve Officer Training Corps (and its members) were more or less [ɹatsi] for me and in the circles I traveled in. This is enshrined in the anti-war-era chant, "ROTC, ROTC, just another Nazi", which only works with that pronunciation. I haven't heard that except rarely in a long time, though, and hear it almost only 'pronounced as letters' in wiki-speak. I can see the former form, especially given the chant, being understood as negative, so that a change could be socially motivated.
Similarly, when I came to Madison back in the 1970s, the Madison Area Technical College was known as [mætsi]. That pronunciation seems to be gone today, and I've abandoned it too after being corrected on it a couple of times.
Are there other examples like this? Maybe these are as odd as weak verbs becoming strong (sneak snuck, dive dove)?* Or maybe the trend doesn't work as sketched above even for these two?
*I'm not entirely convinced that those are as rare as some people claim, but that's a topic for another day.