Just a few years ago, it was widely agreed that the Nexus 7000 would replace the Catalyst 6500 with its superior hardware architecture, modern NX-OS software (which addressed all the limitations of the Catalyst 6500 IOS-SX software), and offer multiples better performance and throughput.
However, it seems customers are voting with their wallets and continuing to buy the Catalyst 6500 platform--and asking for upgrades. After moving $46 billion dollars of Cat6500 hardware in the past decade, Cisco is giving customers exactly what they're asking for.
It's not clear whether customers are actively rejecting Cisco NX-OS software, but the supposed golden boys of Nuova Systems may not be nearly as golden as some people made out if the Cat6500 continues on for another decade while duplicating the same features as the Nexus product line.
The Catalyst 6807-XL is a hardware refresh of the venerable Catalyst 6500E. The backplane now handles up to 880GB per slot. However, with only seven payload slots in total and five effective payload slots usable, it is smaller and less useful than it might have been. Cisco says the Cat6800 is targeted at the campus core, and the lower density meets the requirements for a LAN environment outside of the data center.
The Cat6807-XL is backwards-compatible with some line cards so customers can retain their investment. Given that 60% of the cost price of a Catalyst 6800 is the supervisor modules, this isn't really "investment protection" so much as not wanting to throw old stuff away. It may also be a reflection of funding problems inside your organization--but that's hardly Cisco's problem.
Cisco also announced two other form factors in the 6800 line. The Catalyst 6880-X is a half-size unit using a new half-width module format and fixed supervisor engines. Although it runs the same software, it's not backward compatible. And then there is a Cat6800ia, a 1RU switch. Both of these look more like a custom product build for a large customer than a serious product announcement. It's much more practical to use Catalyst 3850 or 3750-X series switches in the campus LAN.
The IOS-SX code train continues to power the Catalyst 6800. This version/strain of Cisco IOS has a monolithic kernel architecture that dates back to late 1990's and has been consistently derided by engineers as buggy, leaky and inconsistent. That said, it's familiar to legions of Catalyst 6500 customers, which is why Cisco kept the IOS-SX in the 6800 platform.
But this also puts Cisco in an odd position regarding its Open Network Environment (ONE) initiative, which aims to provide a consistent API across all its software platforms. IOS-SX was never scheduled to get ONE support because the software architecture is incompatible, so don't expect SDN to work on Cat6800 anytime soon.
By contrast, the Catalyst 4500-R platform was recently upgraded to IOS-XR to take advantage of multiple CPU cores, modular operations and modern development toolchains. The ISR–4451-AX and ASR1000-AX, which are getting significant hardware refreshes, will get ONE support through the newer IOS-XR firmware.
Cisco is big enough to act like a merchant silicon manufacturer. The UADP silicon that drives the Catalyst 3850 wireless/wired convergence strategy has found another home on the Supervisor 8E module for the Catalyst 4500 for those who prefer chassis-based approaches. The wireless/wired convergence in the enterprise is major theme, and Cisco is covering a gap in the market with this product.
The Catalyst 6800 platform upgrades would have been exciting three years ago, when the extra performance was sorely needed. Cisco emphasized the backward compatibility with existing line cards and modules as a key buying trigger, but you'll have to wait until 2014 before they ship in volume.