We are currently doing a Cisco vs Avaya review since we are mostly 5500's and 5600's. We would have had a significantly higher 4800 presence if the routing table had been bigger from the start, and would have been replacing L-3 5520's with 4850's many years ago.
My expectation is the Avaya technology will live on either as a separate entity or as part of another company's portfolio.
Others in the local area have no plans to stop buying Avaya Voice products, and others are still actively purchasing Avaya Data products, so I do not think the hardware is not going away in the near (1-5 year) future.
My take on it is if the sale of Contact Center goes through as reported by WSJ, the debt will be reduced and the management associated with said debt will follow the 'Crown Jewels' out of the HW side of the house. That should make life easier for the HW focused (Bay/Nortel/Radvision) remnants, who have always been thinking long-term.
What hurts is how badly Broadcom is treating Brocade - it makes investors believe Networking has no value.
BTW, my spreadsheet for comparing the two vendors goes into excruciating detail, down to cost per port when fully provisioned, BTU/power requirements, packet rates, fabric/VSS/L-3/Netflow, etc. I could not just say "3850 = 5952" and have a clear conscience.