Will the cards change?
Good game design may require balancing changes, so cards are always subject to change. This is especially true in the Alpha Phase where there may be balance changes more frequently.
This is the main purpose of the Closed Alpha testing phase. Statistics will be collected during gameplay and feedback will be sought from players.
All this qualitative and quantitative data will be analysed, and tweaks will be made throughout the Alpha and Beta phases. The team will ensure there is a thorough, iterative process in place to perfect the balancing before the main release.
Yes, the metadata may change at any time to keep the game balanced.
Within the Alpha testing phase, anything can happen. Game developers have Alpha and Beta stages to make sure the game is tested to its limits so that the full release will be a good as possible.
You will probably see a lot of changes to cards between Alpha and the full release. Some of the game mechanics may also be adjusted if necessary.
The Closed Alpha phase will be solely focused on gameplay and seasonal leaderboard Ranked Mode. Only when the team is satisfied will the game move into the Beta phase to focus more on other aspects such as the economy, crafting or another expansion card set.
Reminder: the game is still in development and all elements are subject to change.