I would disagree. Though I wont predict where the next world record will come from, I think it will happen, and I think there are deer out there that are bigger. Just think of how many animals (overall) live out their entire lives and are never seen, or very seldom so.
The reason I think it will happen is because in 2000 my friend shot the world record pronghorn. In 2002 the record was tied. Both antelope were shot in AZ. The same year (2000), or it may have been 2001, another antelope was shot that was bigger then the current world record (before my friends was official). Neither was from the same area/gene pool. The year after my friend killed his antelope, we saw at least two that looked as though they would beat his. So, within a three season time period, in three different locations in AZ, the world record antelope from the 1980's was beat. Plus, another year or two after these antlelope were killed, GF tagged an antelope within the same area, they measured that was bigger than the world records.
I certainly think and believe there is always something bigger running around than what is the current record for all species. Remember, before these records were killed, the genes were at some point passed on to others. Just my opinion.