Do you think we'll be able to keep our rank and possibly gain a border after TFT Beta

Beta is basically the final official game release in any gaming environment.

It's called Beta simply because it's the second release after the primary trials.

Ie....... Betas don't end. They just get expanded on. Sometimes people consider ~ 6 months after Beta to be the end of Beta.

What WILL end is the "Beta PASS" which is the event with the tiers/rewards for playing it.

Soon you'll just be queueing up to play, not get free emotes/maps etc.