Tell me what company gives their existing customers freebies. You might get an offer if you renew contracts, but thats about all.
Every year my insurance renewal goes up..I go on to the internet to get a quote. The same Insurance company offer far better deals to NEW customers. Ask them why you cannot get it and they tell me it is just for new customers. I tell them I do not wish to renew my Insurance/cancel it and trhen sign up again at the new quote.
So when your contract is up, then is the time to demand something or be prepared to move on to pastures new.
Further to what toekneem has said, the time to try an negociate a discount on your BB is when your contract is about up, if you are in an area where there are other ISP's, you are at an advantage
You could also try blagging kit from them then.
because no company will buy everybody new equipment every time they change the design !!!!!!!!!!! it may look different but it works and bt provide broadband to you and it wont change just by having one that looks nicer.
sky dont give you a new router/ box every time the change something on it
Sky do not offer you NEW boxes for FREE, and Bt Home Hub 1, BT Home Hub 2, BT home Hub 3 and i believe at least one of those had a least 2 versions. And like as already been said, every time your contract is up ask for what you want. You may get it, you may not. You don't know untill you try.
When I want something, I make sure I have a backup plan first and If I don't get what I want, I make use of that Backup plan.
 I will add that loyalty does not come into it. I am sure that if Sky or Virgin or whoever came along and said to you we have this fantastic offer, you would consider it.
As mentions there has been different home hubs launched with updates every year or every other year. Bt already offer the new hub at half price for exisiting customers. i guess everyone wants something for nothing