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

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 roadmaps to migrations. We hope to work very closely with Informatica and develop and test the best practices as soon as Informatica announces new releases. In a highly unlikely scenario where our customers require migrating ahead of our having certified the rules against the new release of Informatica PowerCenter, we will discuss this with the customer to provide them a least disruptive course of action.