I can't give away too much here, but we had bought some companies and had to change our Web stack to show that we ate our own newly acquired dog food. That part was unavoidable.
I just assumed we would make a gradual transition, replacing the two stack layers one at a time, and starting each of those replacements with new, non-strategic web apps (ex: a mailing list signup sheet for some small event), always getting things working before extending the rollout. We would get as many things working as possible by the "hard deadline", and our customers for these new products (who would be developers themselves and would know that these were new products for us) would understand that a gradual replacement of our old technologies was just good engineering, not a sign that our new products weren't good.
But she told me with a smile that we were going to replace all of our Web apps simultaneously with a matched set of replacements showcasing what could be done with our new products (one of which would require using a version so new it wasn't even feature frozen much less production-ready, to show off our coming features) and, as long as we were changing two critical layers of the stack simultaneously, we would change all the other layers, too, right down to the OS and hardware "and just do it right".
And I assumed I was just laughing with her--yeah, yeah, very funny--until we both suddenly realized what was actually happening.
(And, I don't work for her. I was transferred elsewhere, and she was eventually laid off.)