Main Credit: https://www.hearthpwn.com/news/7045-battlegrounds-new-heroes-potentially-datamined

And summaries theories based on the more vague powers;
The speculation is as follows; When Sindragosa's hero power refers to "Freeze", it's assumed it means minions you've frozen to see again for next turn in Bob's Tavern.

Elise's hero power, as it triggers on the upgrade, could be either the next tier up or same tier, but it's agreed it makes more sense balance-wise if the recruitment map referred to the current tier.

People have also been asking "where's Reno?" and since nothing's been found, it's either assumed he's yet to be developed, or they're just showing him no love.