I seriously doubt you're going to get five justices to rule for incorporation using the P&I clause. It would definitely be nice, but I kind of doubt it.
More likely you're going to get 2 or 3 to vote based on P&I, with another 2 or 3 to vote based on due process. This isn't optimal, but it's still good; a split majority decision on why it's incorporated against the state still means it's incorporated. It just doesn't overturn Slaughterhouse.
One good thing about the P&I argument is that we may get one or more of the liberal justices to vote for incorporation using it, giving a 6-3 or 7-2 majority; the left has been looking for a way to overturn the Slaughterhouse case for a while, and many are willing to team up with gun rights organizations in order to do it.