It won't. An unperked M4 at ENY 15 means it's available more than 90% of the time. And as the M4 can quite easily thrash the Tiger, it will be extremely popular again, just like it was before it got perked. ENY is only a minor consideration to majority of players.
If perk farming was a major consideration, we would see much more T34/76s. And the best perk farming GV is actually the Wirbel. Nothing can get you more perks per invested time.
Maybe I wasn't clear. I did not mean to unperk the M4, but rather have the M4 and the T-34/85 be the same 15 ENY, but the T-34/85 would be unperked.
IMO the reasons the T-34/76 isn't used much as a perk farmer because its gun is horrible for long range fighting and the views are awful. The average/general GVer is lucky to get one kill in it before being killed himself.
The Panzer is powerful enough to be used as a minor perk farmer if it has an opponent it can reasonably defeat that has a better ENY score, but is unperked and therefore likely to be found in some numbers. Right now there is no such tank.