Dated items

[Kiara1]

They'll be back next year's Valentione's Day, no worries. :3

Yaay like 10 months until I'll look pretty! Can't wait!

[Aegis]

Those were event items. So it is possible they will return next summer if they do what they have been doing with other event items from 1.0

This. They don't want any/many items to remain exclusive.

It's sad from the perspective of someone who had hoped to have something special that others can't get, but it's probably a good thing from the perspective of those who see something and say "Cool! I want that"

I think they probably added the summer-wear as a rank 1 reward because this year will be Yukatas and I can promise you there will be a shit storm whatever year they change the rewards from previous years.

"I want a bikini! I don't care about this sucky Yukata"

The following year:

"Last year they got cool Yukatas! How come I can't get one this year?!"

It was the same in version 1, and the beta forums were full of people bitching that they wanted legacy rewards and that there should be some way to get them (well, they have the Goobbue mount now, so they're part way there).