If it levels up with a plate, it evolves into that type. If it levels up again with a plate, it evolves, with that as its secondary type. If it has the same type plate, its final stage only has 1 type. So only 1 pokedex entry for each stage, but 17 forms for the second stage and 289 forms for the 2nd stage (All palette swaps). The typing would be permanent.
Currently awaiting: Pikmin 3, Lunar Knights 2, LM:DM, AC:NL, XY, X, WW HD, LoZ U, LR:FFXIII, FFVXIII Skarmory would slap the hell outta you