No, Lemmy is nowhere near big enough for that. If it was, it would be simply bought out by one of those companies, and then shut it down, like with XMPP. They have no rhyme or reason to skulk around in the shadows.
In its current state, it is still very much in its infancy. A company would see more threat in the competing social networks trying to copy their model, or people just leaving outright than Lemmy for the time being. Mastodon would be more of a threat by comparison.