I know how that works, please do not assume that I wouldn't know. (Btw. medals are not consumed, so technically they would just stack around for no reason...when all pets are upgraded and the medal upgrades are done, which at some point will happen to every player)
Once again - as of now there would be no need for anyone to catch up and you still would have the difficulty to decide if the achievements for the medals need to be changed, or the ingame mechanics need to be changed to be able to separate between bought/collected (earned) ones. Because in my opinion it makes a difference if I had to earn my achievements or if I just spend some money to get those.
And to make it clear: I'm not against IAP, especially for a free game like TapNinja and I already spend some money for the game to support the dev's and I would do that in the future as well, but I need a better reason than "catch up" for a future update, that we don't know, when it will arrive.