I don't think that's true if the reason a company has left the vendor for given model by making it hard to buy. Enterprise IT is enough of a pain in the butt that people will forego the new shiny to avoid the old painful unless it's genuinely better. As you say though, the best frontier model flips regularly, so companies won't go through the hassle of deploying a model if it's proved horrible to do in the past. They'll just skip that model because their current one is fine.