The previous Fire Emblem expansion passes went on sale recently as part of Nintendo's "fund the tariff legal fees" "Appreciation sale", but I wouldn't bank on us seeing another of those considering the circumstances involved.

As far as value is concerned, from what I understand these are 4 whole campaigns that were originally cut from the game because the developers thought the game would be too bloated. You can argue whether it was a good idea to add content that was cut for a reason back in, but I'm not sure you can argue it isn't worth the money when you're theoretically getting an entire another game's worth of content.