At IPEX on 19th May the Ghent PDF Group will sponsor a meeting on "Is PDF still relevant? How and Why?"
Seems a strange question for a print show. PDF is pretty central I would guess. One reason it seems less relevant is that Adobe have more or less stopped promoting it. It seems very unlikely that MARS will reach a release. There are enough rough and ready ways to go from XML to PDF. Acrobat 10 will probably be another plug for Connect and Flash.
It could be the case that after ten years or so PDF is not suitable for margins on software so is not promoted. But apparently Acrobat is still contributing to Adobe income. There may be attention for other options in creating PDF. Acrobat.com is putting PDF in the cloud. Google docs is another way of doing this and there are several others.
Apart from Flash there is also interest in ePUB as a format. This is based on XML and reflows on mobile devices. The PDFXML Inspector available from MARS / Adobe Labs works well with ePUB. Maybe this will be part of the discussion.
"Pre-Media" could have a wide scope, there could even be IPEX time for workflows including Flash.