First off, Blu-Ray will only be a major force for PS3 sales as long as the PS3 remains a very competitive price Blu-Ray player ... If you want a Blu-Ray player and a videogame system as long as the PS3 is only (about) $100 more than either devices it will seem like a very affordable option. Within 12 to 24 months companies like Apex Digital will be looking to sell Blu-Ray players at (roughly) $100 or less because that is their market position, and unless the PS3 is $200 by then I doubt it will be selling (primarily) as a Blu-Ray player to anyone.
Beyond that the PS4 is obviously in development and there are probably plans surrounding releasing it in 2010, 2011, 2012 and 2013 in order to cover the possible outcomes. This doesn't mean that Sony wants to release a console in 2010, but they do probably have a plan in case the PS3 sales fell to a level where it wouldn't survive much past 2010.
Whether you would like to admit it or not, Harrison's departure probably had far more to do with the PS3 falling dramatically short of expectations even with its improvement in 2008. It doesn't matter what culture you're in, a mistake on the scale of the PS3 typically results in key executives losing their jobs.
