Regarding the thought that shunning could be restricted to some offenses (e.g. apostasy), but not others (e.g. smoking): no, I don't think this is going to happen. That would require the R&F to know which "offense" has taken place, so the policy of non-revealing the cause of DF would have to be reversed as well. But this cannot happen for obvious reasons (it could, and will have legal consequences, if the org makes the personal deeds of a DFed public).
Now, as for the general abolition of shunning: highly unlikely, IMO, unless the WTS decides to make a shift from high-control cult to mainstream Catholic-like religion. This could theoretically happen, but it would need a minimum "critical mass" of members: Let's assume the WTS decides to abolish the shunning rule. What follows is a mass exodus of members that don't believe anymore, leaving behind in the religion only the true, ardent believers. That will mean an instant decrease of membership, even by half.
The fact that a church grows older and becomes more widely known does not automatically mean loosening of shunning rules: The religion of Islam 1,400 years old, and is spread all over the world with more than a billion followers. Still, their shunning policy has not been loosened a bit; and the equivalent of "DFing" there is death, not plain shunning. So, abolition of shunning needs not only time and population, but also influence from secular, humanist, ideas. When that happens in JW-land, let me know