Didn't have a clue how to name this one but here we go:
I'll start off with an introduction to the subject. It's a fact that leaving a ranked game will cause you to lose ELO (regardless of the outcome of the game). However, there's something not everyone realizes about that. The ELO loss will not actually trigger until you leave ToS and re-enter. This is where the main topic starts. Utilizing this, you can actually bypass the amount of ELO needed for a rank-up (kind of, anyway). All you need to do is leave ranked games before you lose and queue up again. This way, you'll only gain ELO and the losses will not kick in for the time being. Now, once you've reached the desired rank, you can go ahead and exit ToS. Now after you rejoin, your new rank will remain, only your ELO count will decrease.
The attached example isn't all that extreme, since it's a difference of only 9 points, but it should still work with greater values.
Example:
https://imgur.com/ragrh3z