Yes, this is most likely the primary reason for building rides over a period of years. As a Disney shareholder, I do not mind this timeline. The trajectory of a particular stock is heavily influenced by earnings, and being able to use techniques such as "smoothing" helps The Walt Disney Company make sure they are meeting analyst earning's estimates or hopefully exceeding them.
Now, as a fan of almost everything Disney including movies, merchandise, and above all the parks, I do wish new lands and attractions would open at a faster pace. I wish TSL (and really wish SWL) would be open for my upcoming trip in February, for example. While the seemingly slow pace is not ideal, I am excited for the next 5 years as there are so many attractions, resorts, and even transportation modes (gondolas) coming on line! I believe that once the Studios have TSL and SWL open in late 2019 that Epcot will be the park needing the most attention. Hopefully, Disney comes through with more than Rat and Guardians. Epcot really needs more love.