I don't think too many people around this board will be surprised if I say that my primary reason for seeing them (every single night that they are going to play in the UK regardless of whether it's London or not and also hopefully L.A.) is to see Lindsey.
I am primarily a fan of LB, so even if he leaves FM and joins the Flying Elvis's in Las Vegas, I will go there to see him sing and play with them.
(On the other hand, if Fleetwood Mac were to tour without Lindsey I would probably not go, or go for one night at the most.)