I think Lions release and the "early adopter" base might be quite a bit smaller than Snow Leopards. While SL provided an optional installer for rosetta, from what I hear Lion will not include it in it's initial release (or not at all) ... I am not one of those affected, but from what I see there are plenty of people using software that currently has no option for universal binary/etc. That in my opinion will be a contributing factor why people aren't jumping on Lion at launch day.
I do have software which relies on Rosetta, but that will not stop me jumping on Lion. I'll just have a way of booting Snow Leopard for the occasional times I need Rosetta.
Hmm. Bad day for big cats with all this jumping and booting.