You could have also said 'Because the legendaries go at the end' Technically the highest dex number we have currently would be 81 for the 2 'box-art' monsI think it's fairly obvious that Chillarmy won't be the last pokemon in the dex, and considering:
1st Gen: 151 pokemon
2nd Gen: 100 pokemon (including 17 linked directly with earlier pokemon [8 pre-evolutions, 4 branched evolutions and 5 standard evolutions])
3rd Gen: 135 pokemon (including 2 linked directly with earlier pokemon [both pre-evo]
4th Gen: 107 pokemon (including 29 linked directly with earlier pokemon [7 pre-evo )and 22 standard evolutions])
5th Gen 40-41 pokemon SO FAR (including 1 linked directly with an earlier pokemon [evolution])
Remember Pikablue?
1. Light Pink and Hot Pink
2. Heart-shaped
3. Fish
1. Rodent Shape
2. Zig-zaggy tail.
3. Water type after using a different elemental stone on it
Assumptions can make an *** of you and mumptions. For all we know could be an evolution of Fione (that fish thing that was in 4th Gen that's easily forgettable. Probably not even the right name)