That use case isn't yet handled by pg_shard: the plugin currently supports only hash partitioning and what you've described is range partitioning. This is certainly on our immediate feature list, as range and hash partitioning cover a variety of use cases.

However, CitusDB does support range partitioning and has a \stage command that will create new shards from incoming data. If you periodically load data that corresponds to a particular time range (hour, day, week), CitusDB can easily handle creation of additional shards during each load.