By Thanksgiving there is usually lots of new snow on the face and the avalanche danger becomes a real risk. Even if it's not sliding you might encounter several feet of unconsolidated snow so few people attempt it that late in the season. Also, the road to Rock Creek isn't plowed and that will add a couple of miles to the approach by late season.
From my long time observation, big cornices are what feed the couloirs and after a summer of melt/freeze they are often iced up really well by late summer and early fall. The last two winters were pretty slim and as a result there isn't a lot of ice formation up there this year. I've done it during dry years and while we always found some snow and ice cover, the finish will be on rock. This isn't a bad thing you just have to be prepared for more rock climbing than snow/ice. In a good year we'll get ice from bottom to top but this isn't the year for that.
I'd say either get it this fall and expect a mixed climb or wait until May/June when it's snow covered.