Answer: It becomes a queue when work is committed to a series of program increments!
Let’s say that you’ve committed a set of work to a one-year roadmap consisting of 4 program increments. What happens next is a queue of features … the first feature in line — after the last committed work — will have to wait for, using this example, 1 year for its turn!
It is wise, therefore, to avoid making your roadmap a queue by committing to one program increment at a time… make the rest a forecast. Plan to re-plan! Take advantage of the power of Product managers and product owners to prioritize frequently and constantly … and determine the right sequencing of work at will. This way, no need to commit to multiple program increments. However, do planning / road-mapping thinking process just the same…but always remain flexible — do not be dogmatic on following the roadmap/plan: instead, observe and adapt to the situation.
A famous American general, Dwight Eisenhower, once said of D-Day: ‘Plans are useless, however, Planning is invaluable’.