Tesla demonstates its new battery-swap capability.

There are plenty of folks who still don’t see much of a future for electric vehicles. Clearly, they aren’t the ones investing in Tesla Motors.

The Silicon Valley battery-car maker reached a critical milestone Monday morning when its shares surged just enough to push its total market capitalization up to an even $15 billion dollars.  And though Wall Street pushed back as the morning dragged on, Tesla stock still was running more than five times its 52-week low.

That means the maker, which only just posted its first-ever quarterly profit during the January to March period, now has a market cap equal to Italian automaker Fiat and France’s PSA Peugeot Citroen – combined.

That’s all the more significant considering that Tesla sold a grand total of about 4,750 vehicles during the first quarter. And while that was a good 5% above the battery-carmaker’s original forecast, that’s little more than the number of Ford F-Series pickups sold in two days and significantly fewer Toyota Camrys sold in a week.

In fact, the maker’s “current share price assumes the company can achieve unit sales equal to multiple times our current volume estimates and attain a 12.5% margin on earnings before interest and taxes,” wrote John Lovallo, an analyst for BofA Merrill Lynch Global Research.

The maker has been nudging into double-digit territory, however, with the Model S battery sedan it launched exactly one year ago this month. And Tesla CEO Elon Musk has promised to deliver even better numbers when the maker dials up sales in Europe, China and other overseas markets in the coming months.

Meanwhile, Tesla is looking to add a second electric vehicle line in 2014, the Model X crossover. And Musk recently told TheDetroitBureau.com that the company is moving forward with plans to bring out a smaller, lower-priced vehicle around mid-decade. It could come in at around half the current price of the Model S, which is generally running between $60,000 and $100,000 apiece, depending on battery range and other options.

Tesla’s latest burst of activity comes as the maker marks another milestone, today taking a place on the influential NASDAQ 100 stock index. That alone ensures the maker’s shares will have a ready mutual fund market. Since the recent announcement that Tesla would take Oracle’s place on the NASDAQ100 its stock has shot up as high as $133.26 a share, though it was settling back into the $130 range in late morning Monday trading.

(For more on Tesla’s move to the NASDAQ 100, Click Here.)

Tesla shares began the year at $35.36 a share, and the company had a 52-week low of $25.52.

“Once the stock joins the index, you will have some buying,” wrote Sandy Mehta, chief executive officer of Value Investment Principals Ltd. in Hong Kong.

The question is whether Tesla can continue delighting investors.  CEO Musk has already sent signals that the second-quarter results will not be as solid as the prior three-month report.  And by some analysts’ forecasts, Tesla would have to be on track to selling more than 300,000 battery-cars annually by decade’s end. That would require it to boost demand more than 16-fold compared to the current rate.

The media-savvy Musk has expressed nothing but confidence. And he has announced a series of steps since the beginning of the year to help overcome the most obvious concerns about electric vehicles. That includes a “bullet-proof” battery warranty, a nationwide network of so-called Supercharger stations that would allow Model S owners to travel long distances with minimal disruptions, and an even quicker battery-swap system.

(Tesla demonstrates new battery-swap capabilities. Click Here for more.)

But whether Tesla can maintain even its current pace remains to be seen.  Joe Phillippi, of AutoTrends Consulting, is one of many observers who caution that the maker might simply be drawing from a limited cohort of affluent, green-minded motorists and that once this group’s collective demand is filled sales could take a tumble.

Don’t tell that to Musk or his board, however.  While Tesla’s market capitalization might have surged from $12.7 billion to around $15 billion in less than a week, the longer-term goal appears to be almost triple the current figure.

Last August, the board approved options that would allow Musk to purchase 5.3 million shares of Tesla stock at just $31.17 a share.  But he won’t be allowed to exercise all the options unless and until the carmaker has achieved 10 “operational milestones,” and that includes a market cap of $43.2 billion.

And why not, suggested a proxy statement released on April 11 of this year.  After all, it noted, Ford Motor Co was worth $53 billion that day, and General Motors had a valuation of $40 billion.  In fact, both of those makers have gained substantially these last three months, which seems to be giving Tesla even more confidence.

The Tesla board placed a 10-year time limit on Musk’s options, so he has a bit of time left to catch up to the industry giants – but he’s already well ahead of smaller makers like Fiat, currently valued at around $7.1 billion or Peugeot, at $2.7 billion.