"Species" is an arbitrary designation. Maybe arbitrary isn't exactly the right term, but it's a label which says 'right now, this is different from that' , whereas over evolutionary time actual organisms will interact and intermingle in ways which (as seen in these comments!) aren't adequately captured by the categories into which we divide them.

Almost every species that has ever existed on this planet no longer exists. Nothing “evolves into something else“. Evolution is simply constant change over long periods of time. Eventually, the thing that used to be no longer exists, whereas the new thing does. It’s a giant tree of change. This is literally what Darwin discovered.

Species can completely disappear because they can be hunted out of existence, climate change can kill them off, natural disaster's can wipe them out.