the dropping prices of RAM lead us to re-evaluate what we consider "data that fits in RAM". at 10Gs it's just more economic, and even if we go up one order of magnitude, the serving speed of redis still makes it economic for a lot of workloads.

Eh...as long as you are ready and able to shard the dataset, fitting the data in RAM is quite possible for TB sized datasets.

You can easily get commodity servers with 256GB of RAM per node x 10 shards. Cluster or not, as per your use case.