Slow and proprietary, which is not a great combination... there's a lot of interesting new ARM SoCs from China that are coming out, like the Allwinner A3x series (quad A7s, >1GHz). It would be pretty unlikely for one of those to show up in the next Pi though; if anything, it'll probably be another Broadcom.
Ebon Upton [0], one of the main folk from the Raspberry Pi foundation works for Broadcom and does SoC. So odds are slim considering that connection probably enabled them to get extreme price arrangements otherwise not doable.
His Broadcom relationship is probably much less relevant now that the foundation has some money in the bank and a product that has achieved wide spread success.
On the other hand: The VideoCore IV GPU used in the Raspberry Pi is the only recent embedded GPU for which (large parts of) the specification are publicly available.
Yeah, which is a shame because I think an Allwinner SoC or similar would also fix the other problems people are complaining about in the discussion, like the slow/unreliable USB and Ethernet and the lack of line-in. (Allwinner SoCs have proper USB and Ethernet controllers and audio DAC/ADCs onboard.)
Some of the Android "HDMI stick" devices I've seen running Allwinner SoCs aren't very fast either. Granted they're faster, but compared to SoCs in cell phones, they're dog slow. The Android builds also always seem to not work in one way or other.
