I'm not certain that git will be the dominant VCS forever, as I'd used CVS, Perforce, Subversion, Mercurial, in various degrees when they were dominant (or at least relevant).

Who knows, maybe Linus will have another epiphany, while Microsoft somehow mismanages GitHub and squanders all the goodwill away. Then, a group of upstarts...

That said, wanting to learn git's internals for the sake of knowledge is fine as motivation.