Convergence of the datacenter stack is basically inevitable. Hardware is becoming commoditized, so that Cisco and EMC are basically building computers dedicated to a single purpose out of the same hardware and, in some cases, the same basic operating system. Since both companies already have expertise in building computers, why not expand that expertise into general-purpose computing and integrate the general-purpose product lines with the special-purpose ones, driving overall sales?
In theory, the customer could even benefit from this sort of arrangement, especially given the pain involved in configuring SAN connectivity--how much better would it be to have kit pre-configured and validated to work with your storage vendor's equipment? The next logical step is for Cisco to start making storage gear and EMC to start making storage switches.