Seems like an extremely narrow window of possibility for actually becoming a problem in the power department.
- has to have relevance over a long period because evergreen keywords are added very slowly relatively speaking (beyond standard timescales, which is their primary balancing focus)
- has to be designed in such a way that it becomes problematic in an eternal format if the evergreen keyword list does gets longer
Odric being able to peak out at one or two more blood tokens than the already extensive potential does not seem like a major issue, especially if that improvement is years down the line when the average card is probably slightly stronger anyways.
I think the major issue is memory problems with the list of evergreen keywords. I would guess not as many people as one might think can just list off every evergreen keyword, especially since they sometimes sunset them (prowess). You can probably intuit many of them, but I can see it being an issue.
https://mtg.fandom.com/wiki/Evergreen
I for example, forget that ward is now evergreen, and also that ability would have to somehow specify that only evergreen static abilities are to be counted (note that actions like "counter" are also evergreen keywords technically)