Yes it does
There is an ending to it, at least, in the Atari Lynx port I played there was.
It took a long time to get to it but eventually you would get to a planet that had a cave you would enter, and at the end was a large Alien Queen (not the one that hangs around corners in the bases). It took alot of shots into one spot on it to kill it. After that the game ends and credits roll.
Now as to the arcade version, I've never played it long enough and I don't have one now to do it. The Lynx port took several hours to beat if I remember correctly. I *think* there was 100 bases you had to fight thru, not sure on that part though.