Hmm... I wouldn't be so sure. It may have helped Sony firmly plant Blu-Ray as the dominant format, but I doubt it really will have helped the PS3.
There are still a lot of people without HDTVs and even for those that do have them, I'm sure a lot of people aren't quite ready to replace their DVD collection.
Also keep in mind that this still isn't clear. With DVD there was no alternative other than the non-competitive Laserdisc or VHS and therefore there wasn't the customer apprehension that there has been with the HD formats.
HD-DVD is still out there, and there are still some big studios exclusively releasing their films on HD-DVD. And isn't Wal-Mart exclusively carrying HD-DVD? I thought I heard that, but I haven't personally verified it.