I'm fairly certain that Japan would not get a "German" Philippines at Versailles. Even if they had occupied it before the American entry into WW1 then the mandate would probably go to the USA, Britain or Australia because of the way Japan was treated at Versailles (see Shandong).
There's no chance that America would get the islands. They didn't join the war until 1917 and by then Japan would be totally entrenched in the islands. i think it's politically easier for the Japanese to retain the Philippines than it is for territory in China because now both sides can get something without it being at the expense of the other. Japan would gladly surrender Shandong if it meant it got the Philippines.
There's also the fact that Japan would be far busier in this war than OTL and might not even give China the 21 demands. The Philippines are going to take far more blood, time and treasure to conquer compared to the few Pacific holdings Japan waltzed into in OTL.