Will my rules/best practices stop working when we migrate to a new version of Infosphere Datastage?

No. The rules/best practices are version independent. However, we provide communication to all our clients on any possible hurdles well in advance and provide road-maps to migrations. In a highly unlikely scenario where our customers require migrating ahead of our having certified the rules against the new release of Infosphere Datastage, we will discuss this with the customer to provide them a least disruptive course of action.