IPO Valuation.
- What we know for certain: nothing. The only time we'll actually know when the IPO is priced. Having said that, there were reports (see for example, here and here) of private sales of Twitter stock earlier this year and late last year at valuations ranging from $9 to $11 billion. The NY Times quotes a WedBush analyst that Twitter is now being valued at $15-$16 billion based on recent private sales.
- Speculation: $10 to $20 billion. See for example, here, here and here.
Revenue.
- What we know for certain: Twitter has under $1 billion revenue. We know that because a company must have under $1 billion in revenue to be able to file for an IPO confidentially under the JOBS Act.
- Speculation: 2013E revenues of around $600 million and 2014E revenues of close to $1 billion, according to this article in the NY Times.
IPO Timing.
- What we know for certain: nothing.
- Speculation: Dan Primack of Fortune writes that Twitter's S-1 may be made public within the next few weeks, and that a 2013 IPO is possible.
Bankers.
- What we know for certain: nothing.
- Speculation: Goldman Sachs is the lead banker. Multiple new sources are reporting this, see here and here for examples.
Overall, all we really know at this point is that Twitter has under $1 billion in revenue. Much more will be known when (and if) its S-1 registration statement is made public.
Here's a link to a good article from the Wall Street Journal's Venture Capital Dispatch blog discussing some of Twitter's private investors, including venture firms Union Square Ventures, Charles River Ventures, Spark Capital, Bezos Expeditions, Benchmark Capital, BlackRock Private Equity Partners, Insight Venture Partners, Institutional Venture Partners and Kleiner Perkins Caufiled & Byers.