Ask yourself a question ......

i doubt "everyone" will be RR10...i am quite sure i won't be, and many other casuals won't be neither.
And there will be alt-chars being made etc.

If groups that already have multiple RR8's get bored in a few months and leave, then so be it.
They aren't a huge part of the popualtion, and their playstyle isn't a benefit to a huge part of the playerbase.
Focussing development ressources to keep maybe 5-10% of your playerbase for longer than a year isn't a good idea if you have other more urgent problems right now that need to be adressed (cough teleporting splitting playerbase 50/50 cough).




While you didn't include a question, let me ask you one: What do you think is a realistic way to stop people from hitting RR10 too fast now?

a) you cannot take away huge RP gains now anymore, after the no-lifes have gotten theirs. That would send a horrible sign to the casual mass and drive them away in droves

b) resetting everyones RPs to avoid problem of a): even worse, almost everyone will be frustrated that his efforts of the last weeks were just deleted. Trust in serverstability will decline. People invest time into MMOs to build something that lasts. Uncertainty of when the next reset happens will probably kill the playersbase (and i really hate that argument, but in this case i am confident that it is warranted)

c) reduce RP gains above RR9 extremely: will just increase the slope of the RP curve (that is already steeper than original, because of diminishing task-returns) and would just shift the problem you mention downwards. (if people stop at RR10 because the gains get too small, cutting the gains earlier would make them stop earlier)