Given the animosity Elon Musk has displayed towards former and current Xitter employees, it should surprise us more that people keep working with him. People leaving him is not surprising. Deciding to work with him is surprising.
Since you say it's a serious question, even though it's pretty unrelated to this thread, I'll give a serious answer.
First, 'xitter' isn't an official term related to x/twitter, so there's no official pronunciation.
'Xi' also doesn't occur in english much at all, so there's not much to draw on. My dictionary just has "Xiphoid", where the 'X' is pronounced as a 'Z'.
To my american-english mind, the obvious sound is "Z", like in "xenogenic" or "xenophobic". Or "xylophone". Basically, "x" at the beginning of a word is always a Z sound if a vowel sound follows, and an "ex" sound in exceptions like "X-Ray" and so on.
The only exception to the above is loanwords, notably chinese ones. In words like "Xian", for example, the "X" is pronounced close to the english soft "J" sound (like in Jacques)
So, summarizing, the majority of native english speakers, I believe, will read that as "Zitter", unless told it's a chinese word. There's no official pronunciation, so feel free to pick your own favorite though. This is english, pronunciations aren't wrong or right, they're just vibes.
