The Chinese are not stupid and have a vested interest in finding the aircraft. It would suit their political purposes to release satellite imagery if they thought there was a high probability that it was the downed aircraft, not only to show the Malaysians that they arent doing a good job of SAR but to reassure their own citizens that they are on top of things.
As for the Chinese being reticent to release images showing their satellite capability - anyone who doubts that if the Chinese can soft land something on the moon, and start off a space station and dont have high res imaging on a satellite are not being realistic.