First up, he shared that updates would come more frequently, and in smaller chunks, possibly including new mechanics and alternate biomes. This could be good or bad, depending on your preference, but it will keep the community more active for sure and add tons of replay value (as if there isn't already infinite replay value).
In addition, he said that in the future they'd like to add mod support and creative mode, but didn't confirm them as definite future additions to the game. Mod support would ensure the game could go on past what the developers want to put into the game.
When you consider that development ceased at one point, but then kicked back up with 1.2 and everything we've gotten since, it's really amazing to think that there could be this much coming in the future.
Read the full interview here: http://www.pcgamer.com/mod-support-and-more-frequent-updates-are-coming-to-terraria/