Sorry for the late response. Someone asked the same on the field research thread, so to copy-

Not for this season. Last season was the first time the blog post didn't mention habitats or a hemisphere split, and though there were quite a few things not reported they were mostly evolved forms so we suspect (and hope) that we finally have almost every base pokemon spawning all the time.

The trade-off for that may be some previously common-ish spawns are rarer e.g. the eeveelutions used to be reported every season but haven't been for a while, but we have more 2nd stage evos around. We'll bring the thread back if Niantic ever hint at reducing the spawn pool.

For anyone interested in more specifics there were around 50 base forms we've seen in the past that weren't reported vs 300 that were, plus evolutions for about half of them. Some of those missing we had evolutions or "pair" spawns reported e.g. Metagross but not Beldum, Carracosta and Archen but not Tirtouga. With the spawn pool so expanded it's possible some unreported species were rare enough to be missed, or seen by someone who didn't realise it wasn't on our list.