I keep saying we don't need more scenery, that there's no more themed items that we need, etc. But I've been repeatedly proven wrong! Yeah, I want more animals and will be really bummed if support ends without a tree kangaroo, secretary bird, ocelot, Tasmanian devil, a few more monkeys and so on being added to the game but... I understand the approach. And frankly, while I do think we have plenty of heavily "themed" items there's still a range of foliage and more generic zoo pieces that could be added to the game.
Ultimately, my semi-realistic pipedream is for them to end the year with two strong packs using the alternating pattern (e.g., summer DLC will be animals; fall DLC will be scenery; and final December DLC will be animals). From there, assuming this is the last year for formal support, free updates, etc. it would be fantastic if they just continued on without free updates and just released animal-focused DLC for another year or two. Maybe with a few smaller prop or foliage-focused DLC packs in-between (e.g., a set of 10-20 new plants from a given region, a pack of signs for base game animals in the new/current design, gardening tools, things to help put together parking lots and so on).
That would really help to round out the roster and would be a pragmatic way to expand foliage options, fill-in the gaps with smaller things that may not fit fully into a given theme, etc. And so long as the DLC are still selling nicely? No reason for them to stop expanding on the paid DLC options.
All that said - I'm banking on the fall DLC being another scenery pack (assuming summer is animals).
Only if Frontier adds a coyote in addition to an unique canid I'd welcome it, the song dog prairie wolf of the backyard wilderness. They have beautiful voices! 
