From my naive and amateur view, the relative consistency result makes NF at least as useful as ZFC, since every model of ZFC can be extended into a model of NF. But it seems it won't make NF all that useful unless:
1. We prove NF is inconsistent. Then ZFC is also inconsistent (and the stars start winking out in the night sky ;)
2. We prove ZFC is inconsistent. Then there's still a chance NF is consistent (fingers crossed!)
I'm probably ignoring more practical "quality of life" benefits of NF, like being able to talk about proper classes, and side stepping Russell's paradox with stratified formulas.
1. We prove NF is inconsistent. Then ZFC is also inconsistent (and the stars start winking out in the night sky ;)
2. We prove ZFC is inconsistent. Then there's still a chance NF is consistent (fingers crossed!)
I'm probably ignoring more practical "quality of life" benefits of NF, like being able to talk about proper classes, and side stepping Russell's paradox with stratified formulas.