You saw something a couple weeks ago? They said they were going to add the ability to spectate into the new client. But that's just being able to right click your friends and spectate them (or whatever game they're spectating). And that's in tonight's patch.
I doubt they're ever going to bring back the featured spectate. As much as I loved it, they probably want to make more money by putting all their screen real estate into advertising esports.
Now I used lolking.net's replays. It lets you filter by champions in the game (and you need to filter by the correct region). And if you don't care about champions, you can always just download the most recent replay. It has almost everything the old featured spectate system had, other than randomness and ease of use.
In the legacy client, I do have to close and reopen the client if I want to actually play a game afterwards. Not sure how it's going to work in the new client (assuming the external replay batch files still work).