Zynga, the leading developer for Facebook and mobile games, will turn in the paperwork for their initial public offering on Wednesday, say multiple reports. The amount of money expected to change hands when the company's stock hits the market is staggering. According to The Wall Street Journal's sources, Zynga expects to raise up to $2 billion, a figure that puts the company's valuation between $15 and $20 billion. 

CNBC's Kate Kelly, who broke the news of Zynga's intentions Tuesday afternoon, reports that Morgan Stanley and Goldman Sachs would underwrite the deal. "The expected Zynga IPO--which could come early this fall, on the heels of a midsummer SEC filing--marks another milestone in what is shaping up to be a euphoric period for Internet new issues," wrote Kelly. Indeed, the last Silicon Valley IPO of this size was Google, which raised $1.67 billion in 2004.

With LinkedIn's runaway success, analysts sound positive. Zynga is expected to bring in $1.5 billion in sales this week from popular games like FarmVille and Texas HoldEm Poker. "Of all the companies we’re looking at, it’s the one we’re most excited about because it’s a real company with real revenues,” analyst Nitsan Hargil told Bloomberg.

Big money aside, another reason to watch Zynga is to catch a peek at what's to come when Facebook IPOs. Dan Primack at Fortune argues that Zynga could make or break Facebook's capacity to support companies built on top of their framework:

The real question is if an Internet company like Facebook can be widely accepted as a legitimate, stable platform upon which other publicly-traded companies can build. Kind of like how the Microsoft or Apple operating systems are viewed today for software makers.

Zynga will be the largest test to date, and it clearly has passed the private-market preliminaries. Its IPO will be the medal round.

WSJ's Shira Ovide reminds us that lots of people get a little too eager about IPO announcements. A Zynga IPO announcement has been expected for months and could still be weeks away.