As some of you might've seen from my past blog posts this season, I like to analyze the flash-sideways timeline every few episodes to try to figure out what it is. To recap, my current theory is that the original timeline, in which Oceanic Flight 815 crashes on the Island and the Losties eventually travel back to the 1970's and detonate the hydrogen bomb, is still intact, and is what we're continuing to observe in the main storyline on the Island. "Whatever happened happened" is still true. The flash-sideways timeline, in which Flight 815 lands in Los Angeles, is a completely separate reality that has nothing to do with any influence by the Losties; since the passengers on Flight 815 were never on the Island, they never detonated the Jughead bomb in 1977, so the Island sank as a result of the electromagnetic release, giving a chance for people like Roger and Ben Linus, Ethan Goodspeed, and Pierre Chang time to escape. Furthermore, my theory stated that this alternate reality, since it couldn't be created by any events in the original timeline, was or will be created by the Man in Black, through some yet-to-be-seen circumstances involving a deal between him and various Losties, similar to a genie granting wishes with unwanted side effects.
The most significant change that's occurred on the show since my last flash-sideways analysis is that characters in the flash-sideways universe are now becoming somewhat aware of their lives in the original universe. Some, like Hurley and Libby, simply perceive it as unexplained memories of things that never happened, while others like Daniel Faraday, er, Widmore, believe they have an explanation for these memories, and some, like Desmond, believe they have a mission to actually do something about it. Daniel apparently believes that the timeline that they're in is a result of a nuclear bomb exploding in the past and changing history, which is contrary to my current WHH-based theory in which the Jughead bomb produced the outcome of the original timeline, not the alternate timeline. However, my current theory still fits with the idea that the flash-sideways universe truly is an alternate universe in which the characters' lives are not the way they're supposed to be, and they're just starting to become aware of that. This means that Desmond is on the right track in helping them to discover their "real" lives. I have no idea how they're supposed to return, or merge the two timelines, but I suppose becoming aware of the situation is a good first step.
The other big thing to note is that Desmond in the original timeline, on the Island, seems to have become aware of the flash-sideways timeline, after Charles Widmore's huge electromagnetic generator apparently zapped Desmond's consciousness to the other timeline. Ever since Desmond woke up from that event, he's seemed completely at peace with everything that's happening to him, as if nothing really matters, even being pushed into a well by Locke, which seems really odd. I think Desmond believes that the work he's doing in the flash-sideways universe is what really matters, and therefore nothing that happens in the original universe matters. I suppose it makes sense if Desmond knows that the flash-sideways timeline is the future outcome of events in the original timeline and that it's going to happen no matter what he does in the original timeline. He's just sitting back and letting things unfold, so that he can set things right in the sideways universe.
As for why Desmond rammed his car straight into the wheelchair-bound John Locke, I have no idea. But I'm guessing it has something to do with his knowledge of the Man in Black taking the form of Locke in the original universe. Could the John Locke in the sideways universe really be the Man in Black having left the Island? We'll just have to keep watching the remaining episodes to find out!