These diesel single cabs would be geared towards construction companies that tow things in my opinion. Not for an RV company with 18k fifth wheels, but for construction use I have many contractors that work for me that use a single cab F-250 to tow a bobcat on a gooseneck trailer or a simple box trailer for tools and such. It will definitely be a limited market. The regular Titan single cab could be use by many more contractors like plumbers and such.The regular Titan looks to be a very capable half ton. I think they will sell well. I can't imagine they will sell many standard cab XD trucks in diesel. The $5k diesel option is a tough pill to swallow on a $50k luxary crew cab. On a $35k or so work truck, it will be way harder.
I guess the problem that comes into play is the overall weight of the titan eats into the payload numbers to keep it under a certain GVWR rating.Realistically it should be around 2500# for a CC & 2800# or so for the SC. A CC SB SRW Gas F250 is roughly 3700# so Nissan could of bridged that gap.