Are champions still contemporaries?

Just curious, but are all champions necessarily contemporary to each other after the retcon?

If yes -> life goes on as usual.

If no -> much more interesting things can happen in regards to story in my opinion. Stories such as one character causing a chain of events that eventually creates another character or having characters deal with the results of a past character's actions seem very interesting to me. I also would enjoy examining the nature of time-ambiguous champions such as Aatrox, Bard, and Tahm Kench and how their presence in the world has impacted the development of other champions.