The expansions have not gone anywhere, so they cannot just "come back". As with any games, there are free things....and there are things you buy with real-life money. If you have reached the cap of the number of free things allowed and you want the luxury of having more of those free things, you have to spend money. The developers are not opposed to offering additional free expansions as the game continues to grow. There was clear evidence of this with the Elvenar chapter, where players were allowed to have an additional free expansion. With many chapters to come, I imagine there will be random expansion offerings.
As with everything, your patience is required
Xelenia