"May or May Not" Redundancy

I may or may not contact you later.

Isn't this redundant? Unless I'm missing something, the meaning can be expressed equally well with:

I may contact you later.

Or even:

I might contact you later.

It can be used to convey the idea of the contact being on a whim, although this would be inferred from inflection as much as wording. Alternatively it may indicate pique on behalf od the writer.

Both of these meanings could be conveyed by your alternative sentences, but I think "may or may not" is marginally stronger by virtue of emphasising the optional nature of the action

There is one particular case that I can think of where it is not redundant at all.

I may or may not be available later.

While it's not immediately apparent, what is actually being said is that a person's availability is subject to change, without certainty as to whether or not it will. What is being indicated is that the possibility of being available is unknown. Where, if a person simply said "I may be available later", would indicate that they definitely know that they can be available later, if they so choose.

In short, there's a greater degree of uncertainty over future events in saying "May or may not". It implies that not only is your choice in action unknown, but your ability to choose at all is also in question.

I may contact you later.

Is perfectly reasonable - and less redundant.

may or may not

Is generally only used in a legal sense. It covers both options and so there is no chance that somebody could argue in court (or somebody else could argue that somebody could argue in court) that it implied they would.