What happens to your replays after the next patch?

Sadly no. you can only watch replays of games played in the current patch.However ,a good thing is that you can make a short video of your favourite team fight ace or solo penta kill. You can do that with pushing the red button (rec) while you are watching a replay. Doing that you will get a video as long as you wish, although it is not reccomended to make it too long. After that you can access this video in the "Higlights" menu which is located in the "Profile" menu.

I hope that helped. Feel free to ask me anything. I will be happy to help. And best of luck on the fields of justice.

Another question, can other players viewing my profile ingame see my highlights and replays if they are on my friend list? Not that I want them too nor don't want them too.