Wiping the server will lead to one of two results:
Result 1:
The population that remains there will not return to it once their progress is wiped, and not enough players will return, hence killing the server entirely.
Result 2:
The wipe completely reinvigorates the server, bringing lots of new players back to the server, establishing a population of 1000+.
If the server was wiped, it is in my view that result 1 would happen - it would kill the server. The reason being, Cataclysm is not a popular expansion compared to other expansion's. I know a few private servers that once had 2000 population, reduced to just 400/500. A recent private server opened up in November 2017, that has only a few hundred players as of today, playing on their Cataclysm realms. If a wipe is truly what players want, then there would be similar private servers, that recently started, that would be in their 1000s for Cata. In other words, you cannot name a single successful Cataclysm private server that has a population of at least 1000+.
Back to the original point: Warmane would need perfect justification and evidence to wipe the server, since wiping the server will more likely destroy the remaining population. The community would need to demonstrate who would return, should the server be wiped. Even then, a poll would not sufficiently determine the population - since players can maliciously choose to select "play if server is wiped", to intentionally cause distress to other players.
From what I have observed recently, I believe only a few hundred (100/200) would genuinely return if the server is wiped. However, I strongly believe that the population that currently play on the server (roughly 200/300), would stop playing on it, and move to another expansion - because thats exactly what I did when the Cata server was wiped, I moved to Wrath.
So, although there would be new players returning if the server would wipe, I believe there are more players that would leave as a result of the wipe, than the current amount of players joining the server. This is demonstrated through similar private servers, and recent population trends of Cata private servers, reduced from 2000+ population to 700/800 population, while a recently opened Cata server (opened in November 2017), only has a population of a few hundred. So if a wipe was what reinvents the server, why has other private servers retained such a small player base?
My conclusion is that the wipe would be more detrimental to Cataclysm, and it should remain as it is, until the remaining population declines further.