Not at all.

First, my comment says "more likely" so it isn't assuming anything.

Second, if we change "more likely" to "definitely", the assumption is merely that the sentence in question is written with the same command of the English language as the rest of the announcement, i.e. no egregiously redundant words.

That definition does not help the argument that "legacy application" is a more likely meaning than "legacy mysql". In the sentence in question, the application hasn't been migrated yet, so clearly it has not been superseded.

That's a good question, but it's hard for me to objectively say how I'd immediately parse that, due to the close examination I've given that sentence.

You definitely have a point, though. How the phrase "legacy X applications" is interpreted likely depends on whether the context is an announcement by a competitor to X.