All product cycles are driven by market competition, at the moment, regardless of attempts by Sony, there are two key players, who are really pushing the game to any degree, because they don't make big money from high end products.
I read yesterday that industry analysts are suggesting that Apple is considering a range of two, perhaps three phones to increase it's market share, as currently their product only really sells via contracts which represent something like 25% of the world market, so the suggested plan is to sell a cut back version that looks the same, but uses tech from a few years back, probably the 3GS tech in a 4 case. What struck me was how big that market was - 5.7Bn people ! Now if the digital camera market is lets guess, just a tenth of that, that's a bloody lot of cameras being sold, so making an extra Â£10 per point and shoot becomes much more critical than making a high end camera that they can sell for Â£500 more than an existing product.
Essentially, until such time that the high end DSLR market is offering little benefit over the ranges below, there is little real business sense in moving forward - I suspect there is good reason the whole current crop range is just 18mp, as it's a good step below the high end full frame products, so once the big step comes, which I expect to be a real step up of at least 25-50% performance gain in a key area - most likely pixel count, expect a rush of step upgrades to the crop bodies, each one being 5-10% each cycle.
Canon and Nikon will have the tech now, but are playing a game of Mexican standoff until one breaks due to a drop in sales of their entry level products. Nikon currently has a tad more headroom, so I expect Canon to jump first, closely followed by a slightly better spec Nikon product.