Another factor is the fact that even with data-collecting programs and apps, the average person still won't be able to make sense of most of the data, at least not in any meaningful way. The amount of information we can collect about what's going on in our body is potentially astronomical, and most (if not all) of those parameters will continuously affect each other in some way. The human body is a dynamic and extremely complex system, and is therefore probably subject to the butterfly effect, at least to some degree.
Because of this, I think another factor in the future of personalized medicine is the development of AI that can continually measure and analyze all this data, in order to clear the gap from micro-level, empirical observations (i.e. your blood pressure) to macro-level information that matters to you (i.e. order a salad instead of french fries, because your cholesterol level is at a 6-month high and your heart is under a lot of stress from that bar fight you were in last night).
Accounting for AI powerful enough to glean meaningful information from huge amounts of data, I'd push my estimate of powerful, personalized medical techniques back from the late 2020's to the mid 2040's. And add the disclaimer that the odds of us all missing several key pieces of information that would affect this prediction are quite high. There are a lot of factors involved.