By now everybody's talking about GMail. A couple months ago it was Orkut. In a couple months, who knows, maybe they'll put out their own instant messaging app like Trillian. Whether they really come out with an IM client or not, isn't the point here. The problem Google faces here is that they can't keep quiet.
Google starts making ready for an IPO, and what happens? Yahoo goes from "Google is a good partner" to rushing out their own web search results. Microsoft/MSN releases a bot into the wild and starts making noise about search, even though they really have nothing but a vaporware search engine. Soon, "expert market analysts" are saying that Google isn't worth a dime, much less the $10 billion where a successful IPO would likely value the company.
I saw more than one company deal with this during the "dot-boom." As soon as you look ready to IPO, your already-public competitors will do anything to make news. Why? Because once you commit to the IPO, you have to deal with a very long "quiet period" and you're basically not allowed to do anything newsworthy. Six months of letting your competition make all the news, do all the product launches, etc.
Google needs to keep launching new services to stay competitive. If GMail is released as described, they'll grab a lot of users from MSN/Hotmail and Yahoo, and advertising $$$ move with them. Google may well be on their way to becoming a portal, a piece at a time.
Given that Google is fighting in 21st century time, for mind share and market share, will they ever get to an IPO? Can Google really keep quiet for six months straight?