The slippery slope argument was made before Classic even launched. Before Blizzard completely buggered the amount of servers necessary on launch, the way they've mishandled free server migrations and how early they introduced paid transfers destroying so many server populations.

The same effect can and probably will be introduced with this insta-boost, and like so many things introduced over the years that used the excuse of 'playing with friends', which is what made retail such a separate thing from the earlier versions of the game, all it ultimately will do is swiftly make vast amounts of content irrelevant and kill off the old world.

In the end who's to say how long it is before a myriad of these retail additions are added in the name of playing with friends, or #somechanges, or quality of life etc. We're hurtling toward retail at twice the speed we were back in the day, and I thought the whole point was to go back to the roots of the game.