In a few companies, the decision has been made not to train the IS staff in the new software, because then they'll be too expensive to keep. This is the fastest way to drop employee morale. As a recruiter, I can tell you for sure, if you train your people , treat them well and involve them in the project, you will keep most of them. If you don't, you will lose all of them. Remember that turnover is costly.
Some companies counter the retention problems with retention contracts.
They should be aware that the most highly regarded accounting and consulting firms no longer do this. Taking hostages is not the way to go . Most people are ethical. They know you have invested in them, and as a headhunter I can promise you, most do not relish changing companies. It takes a lot for an employee to be disgruntled enough to walk.