The two men were recently ordered to begin negotiations by the WBA and now it seems that the two teams have set out their stalls with Zanfer wanting to bring Ioka outside of Osaka for the bout and make him fight in Mexico, granting their fighter the home advantage and giving Ioka his international debut. It's been clear since the bout was ordered that Ioka's team had been planning to make the most of TBS's money to get the bout in Osaka on New Year's Eve as part of KYOKUGEN 2016.
With the teams making it clear they each want to host the bout at home, and with the US acting as a possible neutral venue, it seems like the negotiations for this bout could take a while and with neither team likely to back down without a sizeable offer being made. That could mean that purse bids could occur or that the purse for the bout could be very large for a Flyweight bout.
Strangely the longer the negotiations go on the better it may suit Ioka with Estrada having already been out for close to a year, and may well be clogged with ring rust come fight night.