Maybe instead of taking two years, it will take four, or eight. Would you be surprised if it took ten to sixteen?
But then again 64 years might be just about right. How long ago was it again when we were all supposed to be driving flying cars? I remember in 1992 reading about "holographic credit card-sized storage" cards that were heading to market in "just a couple of years".
Engineers, biologists, and others seeking funding often way underestimate how long things take.
I don't think anyone feels that gene therapy delivery mechanisms are going to be plug and play. Until we master the technology, I'm sure that each attempt at gene therapy will be specifically geared to solving a single genetic problem.
It's like in software development. Often introduction of new complexities doesn't create a linear amount of work to write and maintain it. Depending upon the coupling of the complexity, the extra effort could be multiplicative or exponential.
Seriously, how long have we been hearing about "cures for AIDS". A couple of decades? Now, this particular vapor cure has an extra dependency upon an unspecified gene therapy. It's naive to think that an actual cure based upon this research isn't much further away than the article hints at.
There isn't any reason anyone should spend much time listening to what I have to say about it, but I would expect gene therapy delivery to be increasingly plug and play. My reasoning being, the safety issues are concentrated around transmission so insertion strategies that have a robust story there will be copied. Especially if they are effective. Also, the 'obvious' gene therapy targets tend to be similar mechanisms (approximately because they are available at the level of understanding we have right now).
I don't actually expect this to be available as a treatment any time soon, but I think confident pessimism is probably at least as naive as confident optimism (simply because estimating what is possible is so hard).
By this, do you mean "increase", or should we expect e.g. a process that typically takes eight years to take 64 years or 512 years?