Dragon Warrior IV's PS1 remake was cancelled because... Well... I'll let Justin Lucas answer that:

You knew this question was coming. Dragon Warrior IV. For those who still don't know, what happened, development-wise?

If you don’t know the story you must be living under a rock! Hahahah! I think from the time we announced the cancellation to the time of the merger the message board was FULL of posts calling us liars. If we wanted to lie, I am sure we could have come up with something much more creative than Heartbeat closing up shop wanting to move on. Ask any programmer of any programming language how interested they are in working on someone else’s code. That will give you an idea of what we went through to find a way for us to bring the title to the US.

Please explain to everyone why hiring new programmers wouldn't work.

As I mentioned working on someone else’s code – no matter what language is difficult, add in the fact that DW IV was IMMENSE- Nobody wanted to touch it, it was just too daunting a task – There would be nobody to ask how certain event scripts are handled – how anything is done within the code, Every programmer does tasks differently, and having anyone have to learn what does what on the fly would be daunting to say the least.