While the very quirky ads recently rolled out by Microsoft to tout itself–starring Microsoft Founder Bill Gates and comedian Jerry Seinfeld–got a ton of hype, it turns out there will be no more than than the three already released for now.

It seems the churros have gone cold.

According to a Microsoft (MSFT) spokesman, the Seinfeld advertisements were apparently just a warmup for more to come tomorrow, though the new ones will not use Seinfeld in any significant way.

But they might still feature Gates and Seinfeld could return.

But the main Seinfeld/Gates pairing was, said Microsoft, just a “teaser” for the next phase of the $300 million campaign to tout its beleaguered Windows Vista operating system.

[UPDATE] Said Microsoft in an official statement: “We will be executing the second phase of our advertising campaign tomorrow, as planned from the start.”

The company said upcoming personalities in the new ads will include feel-good author Deepak Chopra, television star Eva Longoria and musician Pharrell Williams, and they will also use Microsoft’s own version of the dumpy PC guy character to attack Apple’s hugely successful Mac/PC ads.

BoomTown is dubious, to say the least, that Microsoft can be more clever than Apple (AAPL) in the marketing arena. And by dubious, I mean its chances are as good as Lehman Bros. rising from its financial grave.

News of the development was first reported by Valleywag, which said in its post title that the ads were canceled, which is untrue.

But Microsoft’s rep stresses that this was the plan all along, to jump-start the marketing conversation, even though the ads have, in fact, not gotten a lot of praise.

You be the judge. Here are the three ads. The first with the churros joke and the second and third visit with a family, combined: