I think the Yamaha's will still be in WSBK, just not run by Yamaha Europe as they were this season, probably in a similar vein to the way Ducati were represented. Moto GP disciplines are very differed to WSBK, very few have managed the leap from one to the other, the bikes are very different, requiring different approaches to setup and rider interaction with the team and machine. If you look at places like Spain, they already have a Moto 2 and Moto 3 championship running, the UK does not, most of the UK's racing is based on production machines, not prototypes. Even in the out going 125 2 stroke class, we are still using Honda RS125's which when given a wildcard in the GP's just don't cut it, they are out of date compared to the Aprilia and Derbi machines from the continent. Until racing in the UK is more encompassing of the GP classes at a top national level, then we will be constantly losing talent to racing in the Spanish championships. This sounds very damming, but we need to take heart in that we have the best production based racing anywhere else in the world, if you want to ride a WSBK, the BSB championship is an ideal spring board, the only country that comes close is Italy, which is evident if you spend anytime in paddock at a WSBK meet, roughly half of the place is Italian. They make great bikes, and an even greater assortment of trick bits.
As for the original question, I will definitely be going on the friday, it's reasonably priced, without it being silly season on prices and how much you get to see.