I have an Upgradeable Stack OTA project that's been built with PSoC Creator Ver3.3 and runs successfully. I've already discovered that if I build it with PSoC Creator Vers4.0 without updating any components the resulting cyacd files for the Stack and Loadable sub-projects are compatible with the launcher built by Creator Ver3.3 (i.e. the OTA update works and the updated program runs OK). I'd like to know if this will still be true if I upgrade the components (particularly the BLE stuff) to the latest under Creator Ver4.0. I can't test this right now because there's a problem building the BLE Stack project that I haven't been able to solve. It seems likely that this would work though since the only components in the Launcher are the Bootloader and the UART, both of which are at rev 1.50 with Creator 3.3 and 4.0. With the original (not updated) components the elf and hex files created by the two versions of Creator are different, possibly due to changes in the toolchain or properties.
Generally, upgrading the components will not break things, as the components are usually pretty backwards-compatible. But, testing would be the most effective assurance for your question.