That's what the XIV dev team is facing, in my opinion. It takes a lot of time to properly integrate new staff and get them working at the pace of existing experienced staff.
Any new staff they added right now would likely not be capable of truly easing the workload on the existing devs for a year or more.
The flipside of this being that if you dont add people as you know your project scope is growing, burnout of one major contributor could mean you're never going to get back on track.

Squeenix isnt exactly built well for hiring anyone with experience to step in. They dont hire non-Japanese speakers in that office, or for any of those design teams (something Yoshi has said repeatedly) and they're required to train from the ground up.