Like every other set like this - you complete it next year if you missed out this year... and how many people have hoarded the bonds received on the event? Every time I got enough bonds for 1 extra spin, I took it. That is the way I got the whole set on all my worlds. I worked hard for it and don't see why the instant gratification mob who missed out should be able to buy it.
I missed out on Valentinus set, but, that's life.
I spent every bond I had, plus those I gained in the event, and still failed to gain the whole set on any of my 3 worlds... guess I am not that lucky
and who is to say they will come out with the same set again next year... knowing Inno, they will change it