Tegra4 has taken too long to come to fruition. I know that Nvidia made a statement that they chose certain company/product decisions in order to not have another "tegra 1-3" fiasco by rushing the product. But I think they lost a lot of the device market in the interim which could put them at a disadvantage for whenever T4 comes out.
The other troubling thing is that it sounds like most phones and tablets in the general mobile market are going to be using the Tegra4i, which is using an old ("old") architecture, and is not faster than the Snapdragon S4 pro. The danger with this is that the Snapdragon line will also be undergoing development, and I would be shocked that within a few quarter there isn't something significantly faster than what was released last year, more on-par with the Tegra4.
Competition is great for consumers, but I wouldn't get my hopes up with T4.