I think this deserves it's own thread, so I moved the relevant posts here (and I didn't lose any!
When Pres. Benson died after a long period of declining health and not being seen in public the church membership was 9 million. Today it approaching 16 million. That means a large portion of the membership are very used to having a prophet at the helm, speaking in GC and clearly in charge (from that point of view). Pres. Hinckley was an exception to the rule of declining health, and had himself been called into the first presidency (as a third councilor) because of the incapacity of Pres. Kimball and his counselors (Romney and Tanner). Prior to that Pres. McKay also had a long period of being incapacitated. I was not around for McKay, but I do remember Kimball and Benson very well, and though Hunter's tenure was relatively short he was also not healthy. I think this announcement, which is more open and forthright than I recall in the past, is good because it admits what most of us figure out to be obvious - incapacitated people don't actually go to meetings and watch GC on television in their apartments (it might be on, but they don't know it).
1. In the past when we had incapacitated presidents (the most recent more than 20 years ago) the church continued to run and the membership saw no difference except for speaking by the FP. We sometimes use the term Q15 here, and in reality that's an appropriate term for how it works - the church is not ruled by a dictator who speaks to God on his own, rather it is ruled by committee and any revelation is received collectively.
2. I think the "follow the prophet" rhetoric has ramped up over this 20 year period, and this idea that the prophet might not be really doing the work might shake some. As I said, I appreciate this announcement but I think we still will hear "Pres. Monson was consulted about this decision" whether or not he actually was able to comprehend what he was being consulted about. There are those who will believe that God in some miraculous way helps Pres. Monson to be lucid during those consultations or advisement and I believe that could happen but likely doesn't. I think this will be an interesting period of adjustment for some.
In the absence of knowledge or faith there is always hope.
Once there was a gentile...who came before Hillel. He said "Convert me on the condition that you teach me the whole Torah while I stand on one foot." Hillel converted him, saying: That which is despicable to you, do not do to your fellow, this is the whole Torah, and the rest is commentary, go and learn it."