Apple has released and update which brings the new features of the recently revised Time Capsule and Airport Extreme to the last generation.  The updates also resolve some stability issues.  See all the details after the jump:

 

 

For AirPort Extreme (Early 2009) and Time Capsule (Early 2009) that ship with firmware 7.4, the firmware 7.4.1 update:

– Resolves an issue in which a client computer may be disconnected when waking from sleep
– Addresses an issue in which redirecting SMTP port services may disable IP-layer networking
– Improves the reliability of Back to My Mac-based disk sharing
– Includes recent AirPort security updates

For AirPort Extreme with 802.11n (Fast Ethernet), AirPort Extreme with 802.11n (Gigabit Ethernet), AirPort Express with 802.11n, and original Time Capsule models, the firmware 7.4.1 update:

– Enables remote administration and remote access to compatible USB connected drives via Back to My Mac (except on AirPort Express)
– Improves reliability when backing up to a Time Capsule via Time Machine
– Includes recent AirPort security updates

 

You can get the updates via update in the Airport Utility and see all the details [Here]