I also see the Witnesses going mainstream. However, it will be caused a several factors, internal and external. Of course monetary considerations will be the most important. Their shunning policy, which denies basic civil rights to the rank and file Witnesses, could cause the Watchtower to lose their tax exempt status. Some day it might even be considered a "hate crime." The Watchtower is quick to compromise on issues when money is involved. The length of the District conventions have been shortened because the 8, 5, 4 day conventions don't bring in the money like they used to.
The Watchtower may never adopt the Trinity doctrine and will continue to teach "soul sleep;" but these are not doctines unique to Jehovah's Witnesses. However, I would never go back to the Watchtower no matter how many changes they make.