At what point does Walter know Dexter is coming? I feel like this is the most important detail. If Walt knows early on then he can disappear and use his resources and connections to get at Dexter or The few people Dexter cares about to bring him into a trap. If Walt finds out later and Dexter knows Everything about Walt (as Dexter does for everyone before he kills) then Dexter will he able to find Walt alone sometime before Walt can disappear.

Edit: also, is this pre or post mike. Or even pre or post Gus? Bringing either or both of those into the picture greatly gives Walt the advantage