I guess there are two seperate issues here.
Firstly, to have a CA t-shirt (of any design or year) so that CA members can recognise other members.
Secondly, to have an annual t-shirt, in the same way that the ACO do (as do Team JPC) I personally choose to buy (at least) a new CA t-shirt each year (well, I have done for two years

) but I do think that if it's just the date change next year I may not bother.
I think the first year, several people bought them to have an identity and they were the first ones readily available in bulk. Now that people have "A" CA shirt, I don't think that many people will buy them from year to year (as was the case this year) Also, having polos, sweatshirts, fleeces etc available as well detracts from a single item.
What would the poo bar photo look like next year with a mixture of white and pale blue t-shirts? I know our own team photo looked wierd as half a dozen of us had white CA t-shirts on whilst others had the black team polo on.
Just food for thought!!