I became a mechanical engineer and worked on the Apollo program due to my intense interest in space related things. This was not a problem in getting a meaningful job. But, due to politics in the US, there were times when aerospace was up (both civilian and military) and there were times when it was down. When aerospace was down, in the past, environmental engineering was up. So, to keep my economic position, it was necessary to jump back and forth several times. I think, at the present and in the future, the frequency of this trend will only increase.
As a mech engineer, specializing in combustion related fields (chem, thermo, heat transfer, fluid mechanics, etc), I was able to move quite easily between the engineering field that was in prominence at the time and not wait out a cycle change. I'd advocate a more traditional branch of engineering study to help during future changes in engineering fields.