Yahoo has been sliding for a while. Personally, I never promise first page for any client, and will NEVER promise first page for all top three search engines. That's business suicide in my opinion. While Yahoo remains relevant it is not lip speak these days, and rarely appears in drive by media reporting. Concentrate on Bing and Google.
Google has changed their game in recent months, moving to brand and paid. Bing (at the moment) still seems to serve "ordinary serps" but don't expect that to last long. We are entering a muddy pasture where the road signs aren't as obvious as previous. And we need to let our clients know this as well.