I think in time, the blood transfusion doctrine will fade away very similarly to Mormon's polygamy doctrine. the doctrine met with increasing legal pressure from the state and internal dissent from more liberal members. the tide seems to have turned after the doctrine was about 50 or 60 years old (i am using 1830s as origin date) and from about 1900 on, the LDS church no longer offically sanctioned the belief. of course the practice continued unoffically, and today there are evidently some 30,000 fundamentist mormons who still practice the doctrine, embarassingly for the church.
following that timeline, we are near the cusp of the blood doctrine passing into its decline. in the coming decades, JWs as individuals will probably continue to refuse blood despite lack of support from the organization. new JWs will no longer be indoctrinated in the belief and the practice of refusing blood will pass into the domain of a few 'fundamentalist JWs' who will be an embarrasment to what will be a more mainstream and friendly religion. their past doctrine on blood will be pulled out repeatedly by JW opponents and the WT will insist that it is all a thing of the past.
mox