I think they'd risk losing too much credibility, even amongst JW loyalists.
I think I'd argue that they're not too worried about that. Afterall they did recently redefine the word generation with no relevant scriptural citation (even taken out of context the one scripture they cite doesn't support this 1+1=1 nonsense) and not too many people have gotten upset about it. And most that found a bad taste in their mouth are still trapped because "where else would I go?"
Additionally, it's entirely possible that they've done too good a job erasing 1975 with their revisionist history. The leadership themselves might not realize how big a deal it was. And in 10 years the only people who remember 1975 will be in their 60s at least and at that point I suspect that their mortality and their being unwilling to accept that they've wasted 50 (or more) years on a cult when they should've known better will keep them in. No one else will remember 1975 as anything more than a year that was occasionally mentioned in hushed tones in their youth. If they set a date in 10 years (my personal favorite is 2034, so 10 years would be about the right timing for them to start pushing it) no one will be thinking "here we go again" they'll be thinking "finally!"
Not saying they're definitely going to do it - I can just totally see it happening and I don't think anyone would object to it until after it passed. Even then they'd only lose the ones that weren't helping them much anyway. The very reason date setting works so well is because it's something that everyone should see through right away. The problem is that they get excited before they think rationally and then by the time they stop to use their reason they're already invested and they use their power of reason not to think objectively but to rationalize what they already want to be. After that, no one wants to believe that they've been duped by what is obviously bullshit so they stick with it.