I remember reading and getting that pain in my chest that I had when Nortel filed for bankruptcy.
With that said, we are fully committed to the Avaya/Nortel hardware/software portfolio, including at a greenfield site for a data solution.
Even if Avaya ceased to exist where they could no longer provide maintenance, there is so much used hardware available from resellers and Ebay, that we would just replace failed hardware with cold spares. Some hardware like ERS 8400s would need to stay on 24x7 maintenance from somewhere. But even ERS 4800 and VSP 7000 series switches are becoming quite affordable in the used marketplace.
Overall, we have been very pleased with Nortel and Avaya. We just retired in December two ERS 8600 core routing switches that were in use for over fourteen years. I got a bit of a tear in my eye when decommissioning these switches - that is until we had to remove them from the rack (heavy!).