Yes the 8 host limit for vmfs is still in place, but the Fusion-io cards are non-shared storage.
The issue is: the Fusion-io flashcards are placed in each ESXi host and are not shared with the other hosts in the cluster. Each Fusion-io card will contain a replica which will only be accessed by the ESXi host in which the card is inserted. So technically there is no issue, only one host can access the replica. However, View 5.0 isn't aware of that and is detecting a potential configuration error (a replica on vmfs and a cluster with more then 8 hosts) and didn't allow me to add a 9th host.