Summary: It is not the most common practice for a TCG to add new card type after their release. However, it is not certainly an impossible. Even Magic the Gathering does it e.g. Planeswalker. It looks like Infinity Wars will be adding forth card type in the future.
Above is a part of zoomed screen shot of current beta client deck builder, posted on official forum here.
You see familiar character, abilities, and locations. But there is a forth type called “artifacts.” Currently in Set.1, there is no card with its type under artifact. So yes. this is a confirmation that we will see new card type in the future.