there is no problem aging in the keg. in fact, I would, as you can top it off with CO2 to keep ANY air from contacting the beer, plus a carboy (if you are not using a bucket) is exposed to light during extended aging. i would keg it, put some CO2 on, purge out the air, and age it. then carbonate when ready.
Kegged: Citra IPA
Fermenting: Dusseldorf Alt
Planned: Black IPA, Munich Helles, Belgian Golden Strong, IIPA, Serrano/Habanero Cream Ale...