Was the job offer part of the plan all along?

In the film Snowpiercer (2013), besides population control was Wilford's offering up leadership of the train to Curtis also part of the plan?

I mean, was Wilford planning on retiring and offering the job to Curtis all along, or was it more of a spur of the moment thing just because Curtis had made it so far, and Wilford knew he was getting older?

Wilford even mentions that it was what Gilliam wanted for Curtis, to be in control. But he also says that the original plan was to kill off a good portion of Curtis' people in the tunnel, and then send them back to the end of the train with more space (population control).

If Wilford had planned on offering Curtis control of the train all along, why didn't he put forth more effort into making sure Curtis was not harmed or killed along the way to the engine?