This is what I have gathered while scouring the internets for info about mobile dual cores.
First off Tegra 2 will hold up extremely well for the majority of this year and this is why: (I will focus on CPU and GPU portions of the SoCs)
Tegra 2 uses the ARM A9 architecture which is about 20-30% faster clock for clock against the ARM A8 (pretty much all current phones) in addition the gpu has been shown to be even faster than the SGX540 (in the Samsung SoC) which is already insanely fast.
NVIDIA Introduces dual Cortex A9 based Tegra 2 - AnandTech :: Your Source for Hardware Analysis and News
Nvidia Tegra 2 - Graphics Performance Update - AnandTech :: Your Source for Hardware Analysis and News
Now onto the competition.
Qualcomm has two chips that I should mention, the MSM 8x60 which should be out anytime now and the MSM 8960 which realistically wont be seen until the end of the year.
The 8660/8260 (cdma/gsm versions) will be dual core procs based on the A8 architecture. So even at 1.2 GHz compared to the 1 GHz tegra it at best will be on par and at worse a bit slower. It will also have the Adreno 220. Now this is speculation on my part but I expect it to be better than the SGX 540 which puts it in the same league as the Nvidia solution. So to me the 8X60 and Tegra 2 are on par with each other but Nvidia is out in phones now!
The 8960 will be a gen above Tegra 2 imo. It will be based on the A9 architecture and on the 28nm process (more efficient with potential for higher clocks) And the Adreno 300 series will also be a great deal better. PS3/XBOX360 levels of performance if their marketing team is to be believed. The only problem is that it wont show up till next year or very late this year.
The Samsung Orion imo will be on par with the Qualcomm 8960 with potentially a more powerful GPU but just like the 8960 it wont be out until earliest late this year. (very little info about this guy that I could find but supposedly ridiculous GPU)
And lastly I believe the laggard here is TI. There OMAP 4series wont be showing up until mid this year and unfortunately for them they will be on par with tegra 2. Options for higher clocked cpu but a possibly worse GPU (using sgx 540 with highest end parts bumping up clock a bit) but their DSP portions will surely shine which is there only plus.