Several times I've used or was involved in designs where quite a couple of parts which went obsolete. Recently, for example, my colleague had to deal with a situation where certain analog chip stopped to be offered in the package we have used, and being manufactured only in the ugly leadless package. Almost always the solution was to either buy a lifetime stock of the parts during the "last buy" period, or to pay the premium price for the remaining stock when we missed this period. Almost never was it worth to make a small redesign of the product - it was either a major redesign or continuing the unchanged product until the stock last. Mind that I always worked for garage-scale companies, never had to deal with volume manufacturing.

AFAIK, there are quite a couple of alternatives for serial FLASH chips from various manufacturers, unfortunately no 100% replacement for the Atmel chips, and what's even worse, none even close to Atmel's double-buffering and small-sector scheme.

JW