Granted, that's a prequel, not a follow up (if that's what he meant). I think the chances of any kind of sequel or 'future' installments are very, very slim; and quite honestly I'd be both disappointed and surprised to see it happen. It'd unravel everything the end arc set up and Walter's comeuppance that was so perfect for the show. Cranston has, many times throughout the filming of the show, stated his own opinions as to what Walt's fate was; it was pretty clear that Gilligan didn't divulge much even to the actor's while filming. My point is that this new uproar (media-wise) over Cranston 'wanting' to return to the character really has no impact on whether it actually is a viable option or not. Unless Gilligan goes against both his word and final vision for the show, Walt is dead and the only spin-off's we'll be getting will be a prequel to the show and/or will show other points of view of other characters during the events of the show. On that note, I really think we will see more of Walter White, but before the events of the show.
But I cannot wait for BCS! I love the character and he's got the perfect balance of idiocy, wit, cunning and revolt that a bus-bench lawyer should have. He's also surprisingly clever when he needs to be, so I'm expecting some serious scenes as well. I truly hope they delve into some of the earlier stuff we saw of him in the show, before and while Walt and Jesse were vetting him (next to the grave). I love the scene when he mentions 'Ignasio' and his boys coming to get Saul to kill him. It sounded really serious and that Saul may have already, as others has said in the past, have a fake name and a 'new identity' from a major fuck up. Of course it'll be great to see new scenes and his 'rival lawyer'.