I believe they stated on a fan forum that we won't have a commemorative kit for the last season, so we won't be donning a different colour or design like how Arsenal did in the final season of the Emirates. I'd imagine some level of commemoration would be added to the kit however, maybe the 1985 v-neck returning, or something very plain like our 1960s kits with the white collar. I think Castore will be fine btw, if they want to offer us the most money to produce our kit than so be it. The fact the owners of Castore are also local helps me support it, and their training gear is pretty good, I've worn it for many years.
What we can expect with Castore is increased prices, the dreaded 'authentic' shirts which all the top clubs have seen, I'd be shocked if we don't release four kits next season as that seems to be the new trend too.