It does not matter how much you do to improve anything or how great that expansion ends up being. Most of your player base left will leave and most will not come back. Resetting power will be the singular most devastating thing you could do in December.
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The only way to get around that issue would be if the new content was actually good and a path to power levels - something Kepler never managed. I've never been able to wrap my head around how they didnt utilize Kepler as a source for power. There's literally no reason to play Kepler - outside of triumph chasing - once you've beaten it on Brave. It's just slow, doesnt help with power and they've added stupid timers to halt progress.