After looking it up, and confirming on other discussion posts, last in is never first out. If they are your 10th, you need someone else to move out before they'll request a move, something I CAN confirm with my own, as my 10th and final villager Pashmina moved in back on October 23, 2013, and almost 18 months later has NEVER pinged me with a move request. I don't like her, I needed an uchi, she destroyed a field of flowers, if she would have said she's moving, I would have celebrated. Since I declined the other 9, she'll never give me a move ping. Time travelers have said the only way they got their 10th out was to have someone else move first, reducing it to 9. If they were your 9th, you could still get a 10th in, and move them out faster, since they weren't your 10th.