Seeing as Lion implements the AFP 3.3 protocol now, DHX2 authentication is mandatory
Apparently there is a Terminal hack to not require this. Though of course Apple would not expect people to use this with their products.
Time Machine in Lion requires no less than AFP 3.3. Reducing most current third-party NAS's to a doorstop in terms of Time Machine use, until those manufacturers release a firmware update to include Netatalk 2.2 (AFP 3.3 port) they're pretty much dead for Time Machine
Netatalk 2.2 was released on June 9 (
http://www.netafp.com/netafp-netatalk-2-2-0-is-available-437/). Lion is still pre-release software and many will wait for a few point releases for any major bugs remaining to get sorted out and waiting for apps to get updated to work better on the new OS.
Then there'll also be those waiting to see if Apple will relent and offer a physical media alternative to get Lion.
Lion will not be worth upgrading to for many NAS users for a while.
Considering Lion is due for release in July there's still a bit of time for NAS manufacturer's to get Netatalk 2.2 into firmware updates though it may be pushing it to get it into production firmware before Lion's release.
One would expect NetGear or QNAP would be first looking at
http://www.netafp.com/status-of-netatalk-and-afp-support-by-nas-vendor-322/
Having software updates cached by the Time Capsule would be interesting and a good feature. However if they cripple it by keeping a single non-user replaceable hard drive in it then many will remain not interested in the device.
I have an AEBS for my wireless N network, but I backup using Time Machine to a NetGear ReadyNAS unit.
To consider the Time Capsule, I would like the Time Capsule to have two user replaceable hard drives so one could use RAID-1 for redundancy. If one disk failed one could replace it to rebuild the redundancy rather than having to restore a backup of a Time Capsule e.g. to a new one. A good option for backing up the Time Capsule over a network or to a Thunderbolt peripheral would be good.