I'll have the slides ready in a few weeks in a mail-sendable format, but I am not sure if it is right to put them online - people should have to go to the conference to consume the material, shouldn't they? If significant conference material were available online people might stay at home!

You wrote this twice, but he wrote: "I would appreciate it if you could provide a link to the presentation once it is finished." I'm pretty sure he meant after the conference. In any case reading a presentation and attending to it are quite different experiences: in many cases I find slides to be instructive, but without the accompanying speech much is lost. So those who really want to be there will do in any case and there are also quite a lot of people that won't come anyway, maybe because they live abroad.