I'm not sure whether the issues that are occurring at the moment would require a new engine either. Maybe ancillaries (exhaust, bodywork etc) rather than an engine, which may mean they do not actually have a reliability issue. That said, I am not 100% certain that anyone actually covered sufficient mileage to be confident that the engines will last sufficiently to only use 5 in a season.
I expect that at least one team of each engine will take an engine related penalty this season.