At this point I'm not expecting birds to be a big feature, as disappointing as it is. We've seen how well birds can work in other comparable games. However, if support ends this year, there would be no point in adding any WE bird at all. After all, what would be a game that ends with two flying bird species? I also don't think it's likely that we'll see another full DLC dedicated to flying birds if support ends soon, because the tendency in the last two DLCs has been to reduce investments in new animations compared to what we saw before. To me this suggests we won't be ending support with a lot of new innovations (unless of course they're saving resources but that feels like wishful thinking to me).
If support continues for another year, I think it's likely that we will get some DLCs with WE birds like macaws, lorikeets, hummingbirds and the like. If done like with the butterflies, this can bode a promising end for a beautiful game. However, even with another year, I still don't think we will see a new mechanism for full flight or any expansion beyond the usual DLCs. As great as this would be, it doesn't seem to be feasible anymore in the current way games work.
Anyway, I have a feeling that Frontier will make the decision whether or not to continue support before releasing the next DLC. If that one contains WE birds, I'll believe we will get some more this year and the next. If it doesn't, I'm probably going to put my trust in modders to add flying birds and I'll add them to my game when support has officially ended.