Consider this: Oda wrote in his Festa-letter this december that "[...] the battle between that character and that character lead to unexpected results!!" In his Festa-letter from last year, he wrote that "[...] no way!! That person and that person are going to be fighting?!"
If we look at both messages we can make the following analytical statement: There will be a battle bewteen two characters, who we are - as of now - not going to believe to be fighting against each other (- this is why Oda mentioned it will be a surprising battle). We hadn't a fight like that yet, so I do think that this battle will need to happen in the next few chapters.
Furthermore, the result of the battle will have unexpected results, meaning, that the outcome of the fight will initiate a plot-twist that Oda thinks is so important, that he needs to mention it in the Festa-letter. So, after the fight, we will have a situation, which will be unthinkable as of now. And exactly this is the situation, in which these 9 VAs are going to be important.
Interesting to see is that there are exactly 9 VAs - one for every SHP - if we believe that Luffy or someone else does not Blueno someone of the 9 beforehand.
It all is going to look a little like this:
- Fight of that person against that person
- ending of fight
- ending of fight leads to unexpected result
- unexpected result leads to plot-twist
- plot-twist leads to the SHPs needing to fight against the 9 VAs