I'm not very sure how legit the following information is, but as far as I know, the mempool would be way less congested and tx fees would be so much cheaper if all of us turned to SegWit. I have checked the stats about how many % of the transactions are done without it and it was significant. So if the information is correct, the answer would be as simple as "as soon as we go SegWit". A lot of people don't even have any idea of its existence. If I'm wrong, of course, someone please correct me.