Not necessarily. Before Allied Races, adding a new race had this air of being an incredibly time-consuming process that required a shit ton of resources from Blizzard. So whenever a new race was added, it felt like a lot of care must have gone into their development. Then they went ahead and added like 237821058 races in one expansion.
If they were to add a new race now, I'd obviously play it, but it doesn't carry the same kind of excitement for me anymore. I'd just be left wondering why they didn't add it in a patch instead of trying to market it as a big new expansion feature.