The same positive attributes of Russian and carni lines in cold, also equate to positives in warm winters. here is why....
Russians and carni are much more likely to shut down going into winter (and during dearth periods) as compared to Italians. This based on a stoppage of any fall flow, the shortening of days, night time temps, etc. This means the Russian/carni lines do not get stuck on brood as seen sometimes with Italians. And I also know they go through winter with smaller clusters than the Italians. (This smaller cluster is a reason I use insulated tops and smaller box arrangements than what most bulletins from universities suggest, which is way over blown many times)
So what happens in warmer than usual winters? The Russians and carni lines still for the most part shut down going into winter. But the smaller clusters use far less stores than those mega Italian clusters. And they do fine. That means with Russians and carni lines, the risk of starvation is less, and my feed cost is lower than perhaps Italians would have in the same warm season.
I do know that many of my hives now have more brood than they should, or normally have in colder seasons. So I hope the same weather patterns continue.
Warm weather, cold weather, the bees still benefit from the weather whether cold or warm. With Russian or Italian, whatever the traits are, they are magnified one direction or the other just fine. If you like Russians for their cold weather traits, you probably like their warm winter traits also.
I would imagine that southern producers are jumping for joy as their Italians are probably going to come out of winter with much bigger clusters and build brood faster than in recent years. That is good for them and the bee industry.
I checked one yard two days ago. I lost one full size hive and one nuc, out of 40, so far this year. Both had issues and were tagged as goners. So no big surprise. So I think my Russians and Carni bees are doing great.