I think it is unlikely, but based on his 400/600 PRs, I can't say it's not possible. The previous record was very strong and Rudisha broke it, which makes Rudisha a giant. To say Kszczot can break the WR, you have to say he is better than Rudisha, who is the best 800m runner I have ever seen. Over the years I have seen a lot of fast indoor times come out of Europe and the athletes only run marginally better come outdoors. - With all of that said, Kszczot looks real good, but I don't think any of the prudent followers of T&F would say he is better than Rudisha.