Can I transfer backups when replacing a Time Capsule?
From Apple Support Knowledge Base...

Time Capsule, Mac OS X v10.6.3 or later: How to transfer your back up from an existing Time Capsule to a new one

For this process, you should leave your computer in the same room as the Time Capsules, or use one Ethernet cable to connect your Mac to the Ethernet port on the existing Time Capsule, then use another Ethernet cable to connect from the existing Time Capsule to the new Time Capsule.


Configure your Time Capsule for your network. See the documentation
that came with your Time Capsule for information about setting it up
on your network. 
Open Time Machine preferences in System
Preferences.
Slide the Time Machine switch to Off. 
Open a Finder
window. 
Locate both Time Capsules listed in the SHARED section of
the navigation pane on the left of the Finder window.  Note: If you
do not see your Time Capsules in that section, choose Preferences
from the Finder menu and make sure "Connected servers" is checked
under SHARED. 
Select the name of the new Time Capsule in the
navigation pane. The default name is "Time Capsule xxxxxx", with
xxxxxx being the last digits of the ID printed on the bottom of the
Time Capsule. 
Mount the volume by double-clicking the name of the
volume in the Finder window's main section. The default drive name
is "Data". 
Open a new Finder window by pressing Command-N, or by
choosing File > New Finder Window. 
Repeat the previous 2 steps with
the other Time Capsule, to mount it. Drag your backup disk image
from the current Time Capsule to the new Time Capsule. This can take
some time to complete because your entire backup will be copied.
Open Time Machine preferences in System Preferences. 
Click "Select
Disk...", then select your new Time Capsule. 
Perform a Time Machine
back up. 
After the back up, you can remove the Ethernet cables if
desired and configure your wireless network to your liking.