Ok, I've said it before, and I'll say it again. NOBODY here knows Apple's plans. Only a handful of people at APPLE know when things are going to be released. Coming to rumor sites expecting somebody to know cold, hard facts...is silly at best. Though...you could do some research and conclude that sometime in late August or September when EVERY OTHER Merom notebook is coming out seems about right.
...in all seriousness, though, I hope they don't adopt Merom until they have enough processors in stock. To be sure, the Yonah processors in the MacBook Pro are basically good enough for 90% of the potential MacBook Pro customers out there - it's not a deal breaker - so they shouldn't announce it now and force people (college students in particular) to wait until September to receive them.
They should stock TONS up, so shipping is quick 1-3 day stuff.. or release also put a Conroe into a iMac, so Apple has more Meroms to go into the Macs that need it(Mac Mini, MacBook and MacBook Pro)