Adversarial take: if your company says it does Elm, then hires people (who took Elm as part of the decision of joining) and then decides to stop using Elm, why should we push the guilt of leaving to the employee? I mean, it looks a bit like bait-and-switch, and "We the company altered the deal, pray we don't alter it any further".

How is that employees should be loyal to any decision upper management does? What's the limit? What if the company decides to go into JBoss/JQuery? What if the company decides to stop doing software altogether? What if the company becomes a mercenary army a-la-Wagner? Where do we place the line between employee is guilty for not continuing/company is guilty for changing everything that matters?