I really think there'll be an event. Why not? Apple had an event for the new iMacs last year. We'll probably also see something along the lines of iLife/iWork '09 and maybe new Cinema Displays. But what do I know?
Anyway, Apple has been actively participating in producing hype for the new MacBook/Pros since last year and even a bit earlier. Why shouldn't they want to have an event to finally push everyone over the edge? Every new computer or redesign announced after MWSF 2007 has been at an event of some sort. The only times Apple has done things quietly with an Apple Online Store update have been product discontinuations (iPod HiFi, Xserve RAID) or speed bumps (Penryn MacBooks/Pro, Penryn iMacs, Santa Rosa Mac minis, 8-core Mac Pros). So why wouldn't they have an event?