No, that's not how civil engineering projects work.
Firstly, a planning authority will typically have multiple projects and plans on the go at any one time. However, even if we say they only have one, they will start the planning process for the next project, once they have finished their planning work on the current project - i.e. once it has started the construction phase - and they will do so with knowledge of the estimated construction time-line for the current project. To do otherwise, puts themselves out of a job - a very un-government-like decision.
Obviously, the more common-place the technology, the more accurate the forward estimates of demand, capacity and construction time, and transfer of technology from developed to developing nations can mitigate much of the risk-management in this area.
Your last point is incorrect, in that it assumes the onus is on developing nations to shoulder the financial burden of the decision to use renewable tech. The onus is on the DEVELOPED nations (i.e. where *I* live) to subsidise the choice of renewables, if this is the outcome they want. It should not be viewed in terms of what THEY will choose, but in terms of what WE will choose.