An "oil patch consultant" does have the option of going global, or branching out to other aspects of construction such as mining or industrial manufacturing. Depending on the consultant's specialty, expecially if he's willing to travel for work or do business in a developing country, he might still be able to bring in the big bucks. The income will be bursty: a lucrative short-term gig followed by long periods of unemployment. But as a consultant he's most likely used to that.
The oil and gas industry is indeed in a much needed correction phase right now. Interesting that Alberta is being used as an example: their big oil boom, 2005-ish to present, was preceded by a 20-year regional recession that at times deepened into a full-blown regional depression. Jobs existed in the oil and gas sector, but they were scarce, physically risky, and frequently underpaid especially at the executive level. You don't ride out a storm that lasts 20-25 years unless you're already FIRE.
The oil and gas industry doesn't "always" come back in regions where it takes a hit. If it did, the Sarnia region of Ontario would be booming. It's not.
Much of the trouble with the Tar Sands development is the fact it's necessary to get the oil to regions where it can be refined and consumed. That means either to a populated part of the USA, or to the coast where it can be shipped to a country that wants it. For various political reasons, chiefly the extremely corrupt and opportunistic behavior of the provincial government of British Columbia and the general refusal of many people in the USA to maintain the pipelines and infrastructure we've got (much less build a new one), the most probable solution will be an eastbound pipeline to the St. Lawrence or else northeast to the Hudson Bay, which is not ice-free throughout the year. Until there's a way to get the oil to where it's needed, it's going to stay where it is. There's no guarantee-- absolutely zero-- that the political environment is going to change enough to allow that.