When it was 'introduced' on Quilava it was referred to as a Char counter.
They may very well be phasing out/phased out burn. Really it's wasn't that good to start with. Without Heatran Lv. X it was only a fifty/fifty chance of doing the damage, poison will do the same thing in between two turns without the flip.
This wouldn't be the first mechanic that is there for a certain amount of time and then gone the next. Lv X Pokemon only lasted for the DP generation, Primes and Legends for the HGSS generation, we did have a time where we didn't have any ex/EX cards, Light Pokemon were only in one set in history (Neo Destiny), Dark Pokemon were only in a few sets, Delta Species Pokemon were only in a few sets (I want this back so bad), Shiny Pokemon have popped up in various incarnations throughout the tcg history, owners Pokemon have popped up in various incarnations throughout history as well and to top that one some were done in an evolution form and some were in SP form, which was another mechanic that fits this category. One can only guess how long we'll have ancient traits and mega Pokemon. We won't get into the MANY cards that are always phased out in history.