Blackmagic have now started shipping the Decklink IP boards, and the IP Converter.
I have given the Decklink IP a quick test with CasparCG to confirm whether it works, and as expected it worked fine for fill content on current master without any changes needed.
As I suspected, the card doesn’t appear to support the external keyer mode which means it takes extra configuration to get the alpha/key channel to be output.
You can do this with:
<decklink>
<device>1</device>
<key-device>2</key-device>
<keyer>external_separate_device</keyer>
</decklink>
However, in versions prior to 2.4.0, I would advise caution using this as there is no guarantee that this will remain in sync, both outputs will be running from their own buffers, and it can happen that one will fall a frame behind the other.
In 2.4.0 (or current master), the implementation of this was reworked thanks to feat: decklink consumer "secondary" ports by Julusian · Pull Request #1493 · CasparCG/server · GitHub. I have confirmed that this card does support the sync-groups functionality, so as long as both devices you are using are on the same card then the card will guarantee them to remain in sync