Combine JCI's constant agitating of the incumbent players with Softbank being finally allowed to compete on a level playing field, and we finally (hopefully) will see true innovation in pricing and products in Japan. Docomo will no longer be able to relax and rely on government protection.
Compatibility with other carriersSee here for a comparison table of Japanese carriers. Here is a broader table showing worldwide LTE deployment.
Internationally, FDD-LTE is the standard most used. TD-LTE was developed in China and is only used domestically by SBM, and Japan is the only country using Band I (2100 MHz). As far as I can tell, US AT&T is using Band IV (AWS) and will not be compatible with any SBM's upcoming network. This means that, unless Apple uses a multiband LTE radio, iPads and iPhones that would support LTE on SBM will need a specifically tweaked radio.
Domestically, Unlocked Xi devices should technically be compatible with Softbank's upcoming FDD-LTE network (and vice versa). However, it is expected that the SBM will use their newly acquired 900 MHz band (Band VIII) for FDD-LTE, which will be incompatible with DCM. [UPDATE: SBM is using it for 3G currently but plans to move it to LTE in 2014.] Therefore, while devices should be swappable between these two carriers, it may be difficult to get a signal in the mountains or underground (similar to current situation on Softbank's 3G network).
KDDI will continue to use CDMA-2000 for voice, even after starting their Band I 2100 MHz FDD-LTE network at the end of the year, so AU phones will remain incompatible with the other domestic carriers. EAccess (Emoblie) is the only domestic carrier not awarded either a 2100 MHz allocation or a low frequency "platinum" band.