While it’s remained mum on anything pertaining to its IPO — scheduled for June 29 — Tesla Motors tipped its hand today about its forthcoming line of electric vehicles, as well as how it plans to put together its highly anticipated mid-market sedan, the Model S.

Drumming up excitement about the impending $178 million IPO, CEO Elon Musk is shopping the business around to potential investors, including a line of several different vehicles that most people have never seen before (not the Roadster or Model S). It’s unlikely that any of this is set in stone, but it’s interesting to see how the company is selling itself.

Here’s a look at the presentation Musk is delivering on this so-called roadshow.

This new line of cars includes a cabriolet, a van, and a crossover/SUV in addition to the sedan. The Model S platform will be used as the base for all four, according to Musk, but the sedan will no doubt come first. It’s timed to launch in 2012, but if it experiences the same delays the Roadster did, 2013 might be more realistic.

The four-vehicle line is still very much theoretical, much like the line of electric vehicles Tesla says it has plans to build in tandem with Toyota. That deal — which isn’t all that official — is for Tesla to provide powertrains to frames built entirely by Toyota.

In another blog post, Tesla Vice President of Marketing Gilbert Passin described in detail how the $50,000 Model S will be assembled at the NUMMI automotive plant the company just acquired in Fremont, Calif. The process isn’t exactly revolutionary, resembling that used by most major car makers, but it is new territory for the company itself.

The only car Tesla has produced so far, the Roadster, came in the form of a complete body and frame from Lotus. The company only had to drop in its unique drive train. But for the four-door Model S, it’s starting from scratch, making its own body panels with stamping equipment, and piecing it all together at one site, Passin says.

After the body is assembled, the battery pack, motor, axle and rear suspension will be bolted into the frame as one bundle in a single step. This is where Tesla’s expertise lies — the powertrain that will supposedly carry the Model S 300 miles, and from 0 to 60 miles per hour in 5.6 seconds (not quite as zippy as the roadster, but still good for a sedan).

The detailed nature of the post is significant for several reasons. First, Tesla has drawn a lot of criticism for being so secretive about the Model S, especially in light of its public sale. The company is aiming to go public with at least two years to go before it puts out its next major product. Prospective investors would obviously want to know as much as possible about this phantom car that’s supposed to pull the company out of the red.

Some analysts say Tesla doesn’t even have an honest prototype of the Model S yet — that images we’ve seen so far are simply concept cars that could be scrapped and redesigned. But the specificity of Passin’s blog post suggests that this isn’t the case.

Secondly, the manufacturing walk-through leads watchdogs to believe that the NUMMI plant is adequately equipped for Model S production. When the acquisition of the plant was first announced, it was unclear how much more Tesla would need to spend overhauling the space with the right machinery (which would cost more on top of the property purchase). Passin’s post is designed to make it sound like Tesla already has this under control.

The pre-IPO presentation outlines ambitious plans for growth, but with the Toyota partnership still up in the air, and cash flowing out for the NUMMI plant and no other products besides the Model S even close to the horizon, it’s unclear how the company plans to accomplish its goals.

That said, it’s proven to be teflon in the past, bouncing back from a dreadfully low bank-balance, and other apparent catastrophes. Sex appeal and hype has carried it through before, and probably will again. It will be interesting to see if it’s enough to fetch a high share price if and when the IPO goes down next week.