I respectfully disagree with Blaustoise. What we've previously seen in the bot lane does not make for a healthy or fun game. Even now, out of 20+ marksman champions, less than half are being played competitively. By introducing ''non-marksman'' carries to the bot lane, they cut down the already small pool of viable ADC's. Instead of ADDING champions to the available pool in the bot lane, they actually replace them. Several AD carries get retired for the likes of Vlad, Swain and Malzahar, which also happen to promote boring gameplay patterns.
Another problem. ADC's have historically only been viable in the bot lane, with a support to offer peel. What Blaustoise refers to as ''non-marksmen carries'' here are overwhelmingly AP champions playable in the top or mid lane. By giving them another lane to possibly play in or get picked for, you raise their presence and winrate at the expense of champions that were already struggling. Not to mention that you turn the professional LoL meta upside down and offer a substantial amount of ''flex'' picks in champion select, rendering pick order and possible counter-picking completely useless. The champion select game which currently involves several coaches would devolve to ''just pick the best shit available and hope for the best.''
To summarize, unless the Riot balancing team also makes solo ADC's in the top or mid lane viable, they should not be inserting top and mid lane champions into the bot lane. And if they do plan on making marksmen strong enough to solo early game, which they're currently unable to do, they change the established meta over the last 9+ years. While I ultimately agree with more champions being viable in competitive and high elo, Riot's past attempts at implementing just that have been very poor. There's but a few ways to do it right and many ways to do it wrong. Past experiences don't instill me with much confidence here.