For Power infrastructures I can only guess, I only know about transport, but I think it possible that within 20 years we will discover ways to produce massive amounts of energy through various sources, but despite this I doubt if we will ever be able to replace fossil fuels.
The only temporary solution is coal, but the consequences of this on the climate could be so profound that it makes our planet un inhabitable.
For transport we need to move towards localisation of resources where possible, with freight transport organised in the most energy efficient way, this will be mostly sea, some rail and local road.
Cities, suburbs and towns must prioritise walking and cycling, and efforts should be made to ensure that each is a workable community, with adequate access to work, goods and services.
Efficient public transport, probably BRT (bus rapid transit) or LRT networks should link these population centres together.
Rural towns should also be mainly by walking and cycle, but intra-village transport would contnue to be based on small vehicles, such as cars, as public transport is unworkable in the case of dispersed populations.
The costs of travel should be such that it discourages rural areas existing as domitory towns or 'Ex-burbs' as many areas often termed 'rural' are today.
A transport system like would be very low energy, but actually improve accessiblity, effciency and quality of life.