They may delay their decision until the last possible minute: April 11 + 120 days = August 11. But declaring a JV at this point would require a full and complete sharing of all available data on data on Decar. And that is quite unlikely to happen.
I would even venture to say that FPX has already seen the very last Decar data it will ever receive. FPX will be long gone before the PFS is completed, sometime in 2015.