There have been rumors for a while that Apple might buy Tesla, if only because both companies have many similarities (cultures centered around design and engineering, very product-centric, do few things but do them well, etc). Of course, that's not enough to make a deal happen, and while Tesla's electric cars have a lot of computing power, they're pretty different from Apple's computing devices. So if that's all we had, we could leave it there. But there's an interesting bit of news that came out: apparently Adrian Perica, Apple’s head of mergers and acquisitions, met with Tesla CEO Elon Musk in Cupertino last spring. According to the San Francisco Chronicle's source, Apple CEO Tim Cook was probably also involved in the meeting.
This doesn't prove anything, but if we speculate a bit... If Apple did want to buy Tesla, it could certainly afford it. The company has something like $150 BILLION in cash. and Tesla's market cap is around $24 billion. Even at a healthy premium, they could swing it. Musk probably wouldn't want to sell his shares, though.
Forgot to say one thing at Tesla annual shareholders meeting: just as my money was the first in, it will be the last out.— Elon Musk (@elonmusk) June 5, 2013
But it would be possible for Musk and Apple to take Tesla private together, allowing Musk to keep his ownership of part of the company intact.
Who knows? I doubt it's likely, but it's not impossible. And Apple's muscle would allow Tesla to expand even faster and become entirely recession-proof (the 2008-2009 crisis almost killed the company, something partly documented in the documentary Revenge of the Electric Car).
Musk has announced that there will be several high-profile partners in the green US plant, likely including Panasonic and possibly Solar City. Apple has been investing in big green US factories recently, including its Mesa AZ Sapphire venture. (source)
Maybe that's what they were talking about.
Another possibility, probably more likely than an outright acquisition by Apple, would be a partnership. Either for Apple to help make the software for Tesla's cars and maybe even use some of the bigger Apple stores as showrooms for Tesla, or on something having to do with battery technology. Tesla is working with Panasonic on making a giga-factory that would basically double worldwide lithium-ion production. Apple is also very interested in battery technology, and maybe both companies can work together to push things forward in that area.