The rune system might not be the only thing that's changing when Riot overhauls the rune system in a few months. The familiar Keystone masteries that we've grown used to over the last couple years will almost certainly be getting a facelift as well. Riot is looking into taking some of the existing Keystone masteries and moving them over to the new Rune system, where they would likely serve as some of the new Keystone runes.
"Our expectation is that we'll transfer at least a couple of existing masteries, with some modifications, into the new runes system," said Meddler, Riot's Lead Designer. "We've got some in mind already that we've been testing, wanted to throw the question open to you folks as well though. Poll below for which of the current keystones you'd be most interested in seeing translated over, also really interested in hearing thoughts as to why though of course."
What would the practical implications of this change be? Well, the most obvious is that we would, in theory, be getting some new Keystone masteries to make up for the ones that we're losing. If any of these new Keystones proved to be strong, they would obviously be a meta-changing force in themselves, in much the same way masteries like Thunderlord Decree have forever altered the metagame since their inception. A more recent example would be Courage of the Colossus, which replaced the old Strength of the Ages, dramatically changed both the top lane and jungle meta upon it's release. It's not at all inconceivable that such a thing might happen again, especially since the underperforming Stoneborn Pact seems like a natural target for removal.
The other, slightly less obvious implication would be that previously impossible Mastery combinations might suddenly be possible. ADCs, for example, currently need to choose between two fairly desirable Keystones, Fervor of Battle and Warlord's Bloodlust. What if they didn't need to so, though? If, say, Fervor of Battle became a Keystone rune instead of a Keystone mastery, it would suddenly be possible to take both it and Warlord's Bloodlust, which would dramatically increase the power level of ADCs throughout the entire game. Adding the sustain of Warlord's Bloodlust to the skirmish potential that Fervor of Battle offers would take ADCs like Caitlyn or Tristana from a primarily late game threat to one that is suddenly very difficult to manage all game long. Even more alarmingly is the fact that Kog'Maw would then be able to benefit from both abilities simultaneously, which would dramatically increase the power level of a champion that already is on the cusp of being overpowered.
Whatever the case, it's clear that the Rune changes are going to be one of, if not the biggest change that League of Legends has ever seen. Keep tuned in as we learn more about the new changes over the next few months. You never know how many more games you might win by staying just a bit more informed before the new system is released.