Yes there is always the theory we'll see a "region name"_ian Wyrdeer in the future where the line survived.
But at this time they are theorized to be extinct present day.
UNLESS, some how researchers ended up finding a small hidden population of said pokemon hiding within Mt.Coronet, the newly added Underground Hideaways or perhaps a temporal disturbance caused by Dialga??
Or some random NPC is like "look at this weird deer i found, I'd rather have a Sawsbuck, if you have one let's trade"
(btw fun fact Wyrdeer isn't primarily "weird deer" but "wyrd deer" as in the anglo-saxon/germanic word meaning "come to pass, to become, to go" as well as being used in other languages at the time to mean "to be dignified, honorable, worthy, valuable" and so on)
Ways to work around it.