Flixbus started operating on the West Coast last year, and a week ago it began operation on the East Coast. I was wondering if there is some information, official or not, on whether it is planning to enter the Midwest, and if so, then when? I wasn't able to find anything.
If there is a publicly announced plan for expansion I'd expect to find it in Flixbus's press releases, but there's nothing there. There's also nothing there about the services recently started on the East Coast, so it might not be the most reliable source.
If there are announcements on Facebook I couldn't find them amongst the noise. There's a reference on Twitter to the article referred to by the OP, but I didn't see anything else relevant. There might be references in the newsletter they say they send out, but I didn't find an archive to check.
So, nothing in the obvious official sources. Anything unofficial can be ignored by the company if it doesn't suit them.
FlixBus announced their Texas and New York expansions in this Press Release last December. Texas started very soon after it was announced, much sooner than New York which started almost half a year later. They can move quite fast to start routes when the right opportunity presents itself.
So far they haven't announced it publicly, nor do they have any jobs posted that would hint at such an expansion.