There was a live letter that mentioned previous series rewards would become available later, but so far it looks like none have in over a year since CC was added. I took a break for a while and missed a minion in one season as well as a couple mounts and it is truly bugging the completionist in me. Yoshi SAID go take a break, but then you take a break and stuff is unobtainable... come on man.

...and I mean the CC Series rewards NOT the Feast stuff they've already (frustratingly) said will not come back.