Recently we provided another active tool to give you more control of your Overwatch experience: the ability to mark players as people who you don’t want to play with as a teammate. Our initial deployment of the feature only allows you to avoid two players, but we want to increase that limit over time as we become more confident that it doesn’t negatively affect matchmaking.
Refer to: PLAYER BEHAVIOR IN OVERWATCH
Sure they might not have publicly said anything about trying infinite slots, though they have increased it to 3 since they were confident that it wouldn’t have a massive impact.
At the same time that Competitive Season 12 begins, we’re increasing the number of players you can Avoid as Teammate from two to three. As promised when the feature was implemented, we have been watching to see the effect Avoid as Teammate has on gameplay and queue times. After reading feedback and deciphering data, we think adding a slot will help players better control their Overwatch experience while still keeping queue times reasonable. When you add a player to your Avoid as Teammate list, you will not be placed on the same team with that player for seven days.
Refer to: INCREASING AVOID AS TEAMMATE LIMIT
Though i do think it’s safe to say they’re keeping an eye out for it.
With the amount of suggestions regarding avoid slots i think they can’t simply ignore it. They are indeed checking it, though honestly infinite slots is already just a massive step.