So, teleport seems to be next on the chopping block, for mostly Pro play related reasons.
The summoner makes it hard for lanes to get punished (be it mid or top) and makes game stale as you need to anticipate the enemy just teleporting behind you and completely screw you over.
But more than 99% of the players aren't on LCS level and a nerf to TP will impact top lane a lot more negatively than you might think.
Teleport is necessary in top for more than just "map impact"
You need the summoner to be able to recall safely and not give up your tower the moment you leave it unattended.
You need the safety it provides because the bloody Jungler just makes you, and excuse my french, his bitch otherwise.
You need it to not waste so much gold and xp to the tower because getting back to lane is too slow.
And nerfing TP will make top lane even worse to play.
So, if you decide to nerf teleport you need to nerf a few other things:
I suggest two things:
A) A Jungle retuning
Make the Jungler actually have to take risks when ganking, be it by losing xp/gold in their jungle with faster respawn timers, let them not outlevel every solo lane and just waltz into top lane acting like they own the place or just make the Jungle mobs tougher.
B) Make crit items more expensive so that ADC powerspikes are pushed farther into the mid-late game and give the top laners more time to pick up steam and actually impact the game.
Just my two cents on the matter, simply nerving TP is going to have mostly negative consequences on top lane if you ask me.