What goes around...
... comes around, Milky Way. Andromeda is gonna do that to you in 2 billion years or so. It's on its way!
(ok, yeah, they're going to rip each other to shreds due to more similar size, but still. No more spiral, just another big elliptic, undistinguished blob. With an even bigger, fatter black hole in the centre. Kind of like your typical corporate M&A)